1996 Ford Ranger 4.0 V6 have codes P0306 and P0174 need some advice please

I get steady blue spark attaching an old spark plug to no6 plug wire and ground. It was more blue at the center electrode than near the side post. When I turned the truck on it had code p0306. I cleared it and after running at 3300 rpm for a minute it flashed the mil and had code p0300.
Checking for puffs at the tail pipe, at idle had noticeable puff every few seconds or so. At 2200 rpm same deal but smaller puffs. At 3300rpm did not noticeably puff. After ran at 3300 rpm the mil started to blink and got code P0300. The truck was completely warmed up.

Do you think the cause could be a severe leaking of the intake manifold gasket? Especially near no6?

Is there a way to test specifically for a leaking Intake manifold gasket?

I have the parts to make a smoke machine from a fog machine that I talked to you about way back when.

Is there a way to show a leaking gasket besides a smoke machine?
If I knew what the intake vacuum was normally I could use a vacuum gauge to see if it dropped.
Thanks for your help.

Hi, at 3300 rpm it didn't miss, no puffs at tailpipe. I may try to get permission slips to drive it unregistered. That way I can see what codes will pop up. Or will I be able to get all codes standing still? Is there a pattern I should run at?
The smoke machine is connected to the brake booster right?
The best way to check intake is smoke but are there other methods? I can never check by spraying carb cleaner around to see if engine changes. I just don't know what to look for the change is so subtle. I read I can spray carb cleaner while looking at the short term fuel trim, bank 02 is the no 6 cyl right? This is what I will do next. What do you think?

I just read through my previous posts. I think I will check for blue spark at coil too.

I was asking myself why is it taking so long to figure out this issue. Well at a shop they would be throwing new parts at it in rapid succession and would have already determined it's an intake gasket problem by smoking it. I am afraid to remove the intake because I may never get it back together. I have a 1995 Toyota Motorhome with the timing chain job half finished sitting for 4 years. I have all the parts safe but just can't get going on it. There's mechanic locally who wants me to pay before he comes to work on it. All I really need is to hire a helper for $10/hour to stand there while I finish it. This would force me. It's starting to get cold again here so I may not get back to the Ranger for a couple days. Thanks for your help, Pete

Hi again, today I relaced the coil pack but am still receiving codes P0300 and P0174 after driving for 5 miles and idling a little. My friend said it may be a leaking intake gasket near bank 2, Cyl 6. This is what I thought at the start of this thread. I will put my smoke machine together from a fog machine and fish air pump I have. Can I use a square soap bucket about 3-4 gallons instead of a round five gallon bucket to collect the smoke? You told me how to do it in our first posts. I just haven't built it yet. Thanks for any suggestions.

For the intake gasket leak, how can I make the computer stay in open loop, ie not auto adjust the mixture? I read to remove the TPS plug is this ok? I was thinking of using my PC scan tool to watch the short term on bank 2 while spraying carb cleaner. Is this the way?

Hi could you post some pics of your setup? I heard there are self shutoff glow plugs that shut off at too high a temp. Is that what you have? I am most interested in how it screws/JBwelds together. Thanks

Thanks my email is pcmentor29@yahoo. Com. Your machine is 12 volt right? How does JB weld hold up so far with the heat? Thanks, Pete

Hi Thanks for the pic, the black hose goes to the intake right? Is the clear tube the pressured air coming from the fish pump? You can use baby oil right if you can't get mineral oil? How long till it smokes, 2 minutes, 5 minutes, 10 minutes? Have you ever been able to examine a $1000 Smoke Pro? I read I should put saran wrap over the air filter element when testing. Thanks for your help