Ok, so ive had this problem for over a month now...trying to self-diagnose and havent been successful. Maybe you guys can offer me some ideas to look for.

I am AWE stage 3 in an '01 S4. Just put the k04s in. Put an MBC in with k03 software to eliminate the taper until i got AWE tuning kit. The problem began at this point. It has perfect vacuum, but wont build boost. If i get on it really hard it builds boost slowly but the needle bounces up and down on the boost gauge, violently.

I pressure tested, bypassed the N249, replaced the DVs, changed the ECU to Awe Stage 3, changed injectors to greenies. Still cant figure out whats causing it. I changed back to stock N75.

I VAGd and found no codes, just an 02 sensor but that came up long after the problem started. I am not getting throttle cut, the only info VAG is giving me is that requested boost is MUCH higher than actual boost.

WHAT COULD IT BE???

TIA

 

did u replace the TBB? and if you are a pre 2001.5 tip, check the f-hose

 

yea i have the samco TBB and F-hose.

1 of the connections on the f-hose are only connected with a tie-wrap (not a hose Clamp) because i cud not fit it in there.

Is the f-hose high pressure?

What else could cause this car to build boost and it drop (makes the boost gaue needle bounce up and down)

 

what readings are you getting on the gauge?

 

Check the tubing going out of the N75 valve to both turbos. You should have one tube from driver side turbo get in a 2-1 flange with one tubing from the passenger side turbo then one tubing going to one side of the N75 valve. same thing to the other side of the N75 valve. If these tubing have been mixed up during turbo install you wont get boost or lot less then you should. So, tubing going from turbo wastegate togheter then going to one tubing to N75 valve, then 2 tubing from each turbo intake side going into one to N75 valve. Check for that, in my case they were incorreclty installed and i couldn't get more then 7psi of boost. After putting them in the right order i get 20 psi. This may not be it, but you dont have nothing to loose by checking it.
Good luck [8D]

 

could the fuel pump relay or the fuel pump cause this?