I just recently bought a modded A4.

Giac K04 Chip
K04 turbo
5 bar FPR
Bailey's Diverter Valve
Kinetic MS Exhaust Mani
Milltek High Flow Cat
Borla Cat-back Exhaust
K&N air filter

Needless to say, I am quite happy with my purchase. However, the problem is now that I know next to nothing about my car. I've noticed it doing something sort of strange-- it seems the power fluctuates a little bit (most noticable in second gear) and the turbo gauge shows the boost fluttering between 15 and 20 lbs. Any ideas?

 

by that you mean it will hit 20psi and then tapper off to 15psi?

 

no, it'll go back and forth between them, up to 20, back down to 15, back up to 20 a couple times per second

 

im not to experienced with ko4's but from what i hear around here is that it could be a bad n75 diverter valve.
search the forum for this and you will find out more about this part...

the diverter valve also might have the wrong springs in it, the springs determine how much boost the diverter valve can hold...

 

are u saying the boost spikes at 20 but holds at 15
small turbos do that, the K04 cant hold 20 psi all the way through

 

Check the diverter valve and check for boost/vacuum leaks. This sounds like a diverter valve problem or a torn hose. Since you have a Bailey DV, I'm guessing you have a torm hose somehwere. Check to see if the Bailey DV can be serviced...I can't remeber if it can be.