I just bought a '00 TT quattro... 75K miles...I have receipts for a jet performace ecu upgrade, it has borla dual exhaust and a neuspeed intake... The check engine light comes on and my code reader reads P1128...bank 1 trim fuel running lean which I understand to mean that there might be a vaccum, intake or exhaust leak...I erased it yesterday and it came on again later in the day today...this leads me to my questions....1) could I be receiving this code because of the exhaust and intake? (I think that is unlikely, but I figured you guys know more than I would)......2) Does the audi tt have a "limp mode" decreasing the power when the engine light is on, reducing or limiting engine power and performance? (I ask this because my '02 passat 170hp 1.8t seems to have a bit more zip...might be because I'm not used to the tt as well) THANKS IN ADVANCE FOR YOUR HELP!
-J

 

i just got rid of that cel on my 00 tt. get some carb cleaner or starting fluid and spray it around all the vacuum hoses while the engine is running. if you hear a change in rpm's, you've found your leak. mine was in the pcv system under the intake manifold (directly under the FPR). vacuum leak isn't the only cause, but from what I found when searching online, its the most common cause of that cel.

 

i had the same code, replace your mass air flow sensor and your car will run alot smoother and you cel will be gone!

 

check all hoses are on tight and no vacuum pipes are split, P1128 = hose leak

 

p1128 on a 2000 quattro is the Mass Air Flow sensor, i had the same code and my audi dealer scanned me for free and told me i need a maf sensor, so i bought one put it in and cleared the code and have been cel free since.

 

It can be maf, it can be a vacuum leak, or it can even be a restriction on the fuel side to cause that cel code. A vag-com can tell you whether its maf or vacuum leak, but without one I would try diagnosing the vacuum leak first simply because a can of carb cleaner or starter fluid is a hell of a lot cheaper than a new maf. BTW, this is what the bentley manual has to say about P1128:

P1128 17536 Long Term Fuel Trim mult.,Bank1 System too Lean

Check Exhaust system components
Check Fuel injectors
Check Fuel pressure regulator and residual pressure
Check Fuel pump
Check Intake system for leaks (unmetered air)
Check Secondary Air Injection (AIR) system components

 

I had the same code on my o1 tt 225 and that Mas is actually under an extended warranty. I took it in and my car was well out of it's normal warranty and they fixed it for free for me.
Justin