i chiped my a4 a while back and i just put an intake on and a downpipe, my car sounded really good, i was holding 15lbs of boost, all of a sudden i can only hold 5 and sometime it will go to 15 but the it will go back to 5lbs.... is it a boost leak? or the turbo's shot? ... PLEASE HELP A.S.A.P thanks

 

Probably a vac leak somewhere check the line to your wastegate and get it vag-ed

 

could be many things. Your N75 valve could be shot. Maybe a wastegate thats sticking open on the turbo. Maybe a boost leak, but that's a massive drop in pressure only to see it go back up to 15psi again. Could be going in an out of limp mode, although that's highly unlikely. Get ahold of a vag-com. Check for fault codes in engine. This might just tell you right there. If we need to go further then we can log engine blocks 115, 003, 031, 020. Don't worry, your problem will be solved.