running in limp mode...heres my fault codes please help!
 

2001 audi a4 1.8t test pipe, full borla exhaust, k and n filter

ok so my car is running in limp mode at like 4 or 5 psi of boost
i got a buddy of mine to scan the car and heres what i got...

17887- brake boost vacume system mech. malfunction

p1479 error intermittent
16804 catalyst system cyl bank 1
p0420 error occurs intermittent
17536 long term fuel trim too lean
p1128
18010 power supply (b+) term 30 voltage to low / p1602 intermittent
16826 evap emissions controll sys small leak
17522 bank 1 sensor 2 resistance too high
16524 bank 1 sensor 2 no activity

yea so i know its alot but they may be really old so i had him clear all the codes but what do these mean and which once could lead to running in limp mode and any sugestions on what might fix it and get me back to running back up to normal boost? any help is welcome and apprciated

Are you running a DIODE mod, or a chip? Limp mode will only occur if you lean out the engine too much, or you go over the allowed boost of 14 psi. Pop the hood and check the brake booster vacuum line, it could be broken causing your motor to run lean.
Other than that a lot of the codes are intermittent so clearing them was the best thing you could have done. Check the fault codes again before long and see what comes back first.

hey thanks for replying! no im not running a chip or anything...and what u said would kind of make sence since the brake boost code showed up... could u find a picture and show me exactly which one is the brake booster vacuum line thanks again

If you can't find the brake booster line you're in trouble man, its fvcking huge! Just look behind the brake master cylinder, that large black round drum thing is the brake booster. The line attached to it is the brake booster, if its leaking bad enough the brake pedal will feel a little stiff.