2000 Toyota Camry EGR System problem and questions

Have you seen my attachment?
There is a paragraph "My questions". In this paragraph you can see 5 items in bold:
Question 1:
Question 2:
Question 3:
Question 4:
Question 5:
At the end of each item Question1 - Question 4 you can see the questions themselves.
Item Question 5 has 3 sub-items a, b, c. The question itself is located at the end of sub-item c.
For your convenience I attached here my previous message and highlighted with yellow all questions.

Thank you,
Alex

I believe you could not open my attachment because it has 2 pictures in its body and this web site message system probably does not support picture format. The following is what I sent you as an attachment, but now I removed the pictures.

Hello!

My name is Alex and I am looking for answers for a few questions, which, I hope, can help me to fix my car problem.

Information about the car:

Make and model: Toyota Camry 2000 CE;
Engine: 5S-FE (4 cylinder in line, 4 cycle, gasoline);
Transmission: Automatic;
Mileage: 56,000.

Information about the problem:

Diagnostic trouble code is P0401 � EGR insufficient flow detected.
Code itself appears pretty often, but as “pending”, then it disappears. Sometimes, if I do not reset pending code, my Check Engine light is ON, but after a few trips it turns OFF. It can happen and not happen after slow street trips and it can happen and not happen after high load high-speed highway trip. So it happens sporadically, at least it looks like this.

My questions:

My Chilton Toyota Camry 1997-01 Repair Manual, as well as many on-line sources, describes EGR system test procedure as follows:

1. Install vacuum gauge between the EGR valve and the hose from the
Vacuum Switching Valve;

2. Start the engine and connect terminals TE1 and E1 on the test terminal;

a. With the coolant temperature below 131F the vacuum gage should
indicate no vacuum at 2500rpm.

B. With the engine warm it should indicate low vacuum at 2500rpm.

C. Disconnect the vacuum hose from R port of the EGR vacuum
modulator and connect the R port directly to intake manifold using
extension. Raise the rpm to 2500 and verify the vacuum gage
indicates high vacuum.

Question 1: Point b... Low vacuum. How many mercury inches does low
vacuum mean here? I have about 0.2-0.3 inch, is it OK?

Question 2: Point c. Port R of the EGR vacuum modulator is connected
with vacuum hose to port R of the throttle body. If I follow the
instruction, throttle body’s port R will be disconnected at all,
what means it will stay open. Should I conduct the test with
open throttle body port R or I should plug it?

Question 3: Point c. To what intake manifold’s particular place should I
connect R port of the EGR modulator? The intake manifold has
a few points, but all of them are occupied with other car
devices. The most easily accessible point to connect EGR
modulator’s R port is point of connection of MAP sensor.
Should I connect this R port between intake manifold and MAP
sensor using 3-way feature (tee)? I think that due to R port is
connected to atmosphere it can reduce vacuum reading by
MAP and vacuum presence in intake manifold.

Question 4: Point c... High vacuum. How many mercury inches does high
vacuum mean here? I have about or a little bit less then 1
inch, is it OK?

Question 5: I did the following tests:

a. I disconnected vacuum hose from port Q of the EGR modulator (the
hose connects EGR modulator’s port Q and Vacuum Switching Valve)
and connected this port directly to a vacuum gage. Other words I
measured vacuum directly at the port Q of EGR modulator leaving
VSV hose open and all the rest EGR system components
unconnected to the EGR modulator (and so at inoperative condition).
The vacuum gage showed vacuum from 5 to 10 inches depending on
car’s load and rpm.

B. I disconnected vacuum hose from port P of EGR modulator (the hose
connects the EGR modulator and port P of the throttle body) and
connected the hose directly to the vacuum gage. Other words I
measured vacuum directly at the throttle body’s port P, leaving all the
rest EGR system components unconnected to the vacuum source
(and so at inoperative condition). The vacuum gage showed vacuum
from 5 to 10 inches (a little bit more then in previous test a) depending
on car’s load and rpm.

C. I measured vacuum at the same points as in previous tests a) and b),
but I used 3-way feature (tee) to connect vacuum gage. So, all
components of the EGR system were connected and the system was
at operative condition. The maximum vacuum what I could get was
about only 1 inch. So, I saw even small amount of exhaust gas highly
affects vacuum level in intake manifold port P. Is it normal?

My original attached message also had some words and sentences emphasized with bold print what could help better understand it. Due to this web site message system does not show bold print in its message body I also attached here my message without those pictures. May be you will be able to see the attachment with no pictures, but with bold print.

If you give me your e-mail address I will send you my original message with pictures (which can help understand Question 5 better) and you can read it.

Thank you,
Alex.

Sir,

Before I applied to you with my questions I had already done all these tests and even more:
1. I checked that EGR valve can hold vacuum (10-12 inch) perfectly;

2. I checked that if I have engine at idle and apply 2-3 inches vacuum directly to EGR valve the engine stumbles and even stops running;

3. I removed EGR valve and checked that its intake port (for exhaust gas) and outlet port attached to intake manifold are clean;

4. I checked that VSV functions;

5. I found that EGR vacuum modulator passage from P-port to Q- port was clogged with small particle and filter was not enough clean and I replaced the modulator.

6. And finally I found that vacuum from throttle body’s port P is not more than 1 inch.

Because I cannot find how much this vacuum should be for my car and how to test whole EGR system (not its separate components) I applied to you with my 5 questions.

Thank you very much for your information how to check EGR valve, but, as I said, I know this and I already did that. I would like to get answers for those 5 questions I asked.

Thank you,
Alex

Sir,

I appreciate your efforts to help me, thank you very much. However, as you can see, I have already done almost all what you advise me. But I cannot do test for whole EGR system because I have questions where to connect EGR vacuum modulator’s port R, questions what are “low” vacuum and “high” vacuum. I asked you these questions in my initial message to you.
Last message you sent me contains 2 pages of Prodemand website. The first page contains information how to test VSV. I did it before I contacted you and VSV is OK.
Item 5 on the second page refers to exhaust gas recirculation system test. This is the test I could not do, as I mentioned above. Could you, please, send me the article referred in that item 5 as “Exhaust Gas Recirculation (EGR) System Test under Emission Systems & Sub-Systems in System & Component Testing � 4 cilinder”. May be that article can answer my questions 1-4.
Also, please, tell me what kind vehicle these articles refer to: tracks, cars, any particular maker and model. Or these articles are just about hypothetical vehicle?

Thank you,
Alex.

Thank you, sir. I appreciate you try to help me. The information you provide me is exactly the same information I had and it gives rise the same questions. I have no any doubts that these information sources just copy information from each other, even without paying attention that the information is incomplete and with no common sense. I hoped somebody had practical experience or theoretical knowledge to answer my questions.
Again I appreciate you tried to help me, you did everything you could do and now there is no sense to continue our communication further.

Thank you,
Alex.