1998 Audi A6 car codes and related problems

I recently bought a 1998 audi a6 quattro and it had a check engine light so I checked it with a vag-com I recently bought and at first these were the error codes I got:


Chassis Type: 4B - Audi A6 C5
Scan: 01, 02, 03, 08, 15, 16, 17, 35, 36, 37, 45, 55, 56, 76

Address 01: Engine
Controller: 4D0 907 551 AH
Component: 2.8L V6/5V MOTR AT D01
Coding: 06252
Shop #: WSC 02325
1 Fault Found:
16795 - Secondary Air Injection System: Incorrect Flow Detected
P0411 - 35-00 - -
Readiness: 0000 0100

Address 02: Auto Trans
Controller: 4B0 927 156 G
Component: AG5 01V 2.8l5V USA 8509
Coding: 00000
Shop #: WSC 00000
1 Fault Found:
00526 - Brake Light Switch-F
27-00 - Implausible Signal

Address 08: Auto HVAC
Protocol: KW1281
Controller: 4B0 820 043 G
Component: A6-Klimavoll
Note: Excessive Comm Errors

Address 15: Airbags
Protocol: KW1281
Controller: 4B0 959 655 K
Component: Airbag 7 Audi 0501
Coding: 00106
Shop #: WSC 02324
1 fault found:
00532 - supply voltage B+
07-10 - signal too low - intermittent

Address 35: Centr. Locks
Protocol: KW1281
Controller: 4B0 962 258 C
Component: Central Lock/Alarm D30
Coding: 15885
Shop #: WSC 02325
VAG-COM Version: Release 409.1-S

8 Faults Found:
01371 - Alarm triggered by Door Contact Switch: Driver's Side
35-00 - -
01374 - Shareware Version. To Decode all DTCs
35-00 - Please Register/Activate
01370 - Shareware Version. To Decode all DTCs
35-00 - Please Register/Activate
01369 - Alarm triggered by Hood Switch
35-00 - -
01368 - Shareware Version. To Decode all DTCs
35-00 - Please Register/Activate
01373 - Shareware Version. To Decode all DTCs
35-00 - Please Register/Activate
00956 - Key 2
09-10 - Adaptation Limit Surpassed - Intermittent
00849 - Shareware Version. To Decode all DTCs
31-10 - Please Register/Activate - Intermittent

Address 36: Seat Mem. Drvr
Protocol: KW1281
Controller: 4B0 959 760 A
Component: Sitzmemory D05
VAG-COM Version: Release 409.1-S


1 Fault Found:
00668 - Supply Voltage Terminal 30
07-10 - Signal too Low - Intermittent

Address 45: Inter. Monitor
Protocol: KW1281
Controller: 4B0 951 173
Component: Innenraumueberw. D03
Coding: 00001
Shop #: WSC 02325
VAG-COM Version: Release 409.1-S

2 Faults Found:
01382 - Alarm triggered by Anti-Theft Sensor: Front Left
35-00 - -
01383 - Shareware Version. To Decode all DTCs
35-00 - Please Register/Activate

.

so I decided to read around and the clear path was to clear the codes and see what comes up in a couple days. I did that and the car was running fine. The code regarding the engine I believe has to do with the air vacuum hose, which has a recall, so im taking it in. After I cleared the codes the service insp. Light was still there in the dash, but the CEL was gone. As im driving for the past couple days, I would randomly feel as if the car has shut off for a second, the abs and brake lights would turn on, and it would beep and after that second, the rpms would jump back up to normal(so from 3000 rpms-->100ish rpms-->3000rpms) and you can feel it in the car. Also felt like the gears clunked. Now this really scares me, but could that also have something to do with the vacuum hose? Because the recalls main concern was that the hydro brakes fail at low temperature.

so I decided to take another scan and these are the fault codes that came up this time:

VAG-COM Version: Release 409.1-S

Control Module Part Number: 8E0 614 111 M
Component and/or Version: ABS/EDS 5.3 QUATTRO D31
Software Coding: 0273004134
Work Shop Code: BB 24302
1 Fault Found:
01203 - Electrical Connection between ABS and Instrument Cluster
03-10 - No Signal - Intermittent

Control Module Part Number: 4B0 035 186 A
Component and/or Version: Radio D02
Software Coding: 00117
Work Shop Code: WSC 02325
1 Fault Found:
00668 - Supply Voltage Terminal 30
07-10 - Signal too Low - Intermittent

.

can you please help me, and advise me on what I should do. Btw, I dont know if this will help but the when the car shifts in a couple of the gears, the rpms will kind of jump 100rpms and you can hear it, in between the shift but its quick. It has an exhaust leak right before the resonator which im gonna get repaired soon and also the car doesnt warm like it should. For the forst 30 minutes or so, it will flucuate between the 1st dash line(both the engine and coolant) and go right back down to the begining of the scale. Even at times when the coolant will reach the middle, it still at times will go all the way down again. I dont know how normal this is, but I did not recieve any thermostat or heating codes, aside from an hvac code which stated too many comm errors, which I heard was normal. But I dont know. Im sorry for the really, really long post but I wanted to give you all the information.


**recalls of concern**
NHTSA CAMPAIGN ID Number: 98V134000
Summary:
VEHICLE DESCRIPTION: PASSENGER VEHICLES. IF THE ENGINE BACKFIRES DURING A COLD-START, AN AIR SCREEN WHICH IS LOOSELY SEATED IN THE AIR FLOW METER CAN BECOME DAMAGED.
Consequence:
SCREEN PIECES COULD ENTER THE INTAKE AIR FLOW SYSTEM AND PREVENT THE THROTTLE PLATE FROM RETURNING TO ITS FULL IDLE POSITION.


NHTSA CAMPAIGN ID Number: 99V131001
Summary:
VEHICLE DESCRIPTION: PASSENGER VEHICLES EQUIPPED WITH AUTOMATIC TRANSMISSIONS. A CONTROL VALVE IN THE VACUUM HOSE CONNECTING THE BRAKE BOOSTER TO THE INTAKE MANIFOLD MAY NOT OPEN OR CLOSE FULLY AT TEMPERATURES BELOW -4 F UNDER CERTAIN DRIVING CONDITIONS.
Consequence:
THIS CONDITION COULD CAUSE INSUFFICIENT VACUUM TO BE PROVIDED TO THE BRAKE BOOSTER.

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Thank you.