ok so i put a boost controller on my 1.8t a few weeks ago and over that time i saw boost spike to around 18 a few times. yesterday it took a crap and will only build 4 and drop to 2. mech said maybe some valve. idk what. charge lines are all good from what i can see and car isnt smoking. no leaking sounds. what the problem is???

 

Diverter valve most likely. Its got a plastic diaphragm and can't take the elevated boost for long. Best bet is either an aftermarket DV (like a Forge DV) or one from a 225TT - those will hold the boost. You really should be chipped though - by getting the chip, you'll run the higher boost but your timing and fuel curves will be calibrated to properly handle it, rather than the engine having to react to feedback from engine sensors and correct itself.