hi guys, i have a 1999 pre facelift s4 with just over 100k on the clock. it has been chipped, has a cat back miltek exhaust and a boost gauge. when i start the car for the first time in the day it idle really rough and sounds to be misfiring, when it is doing this i can feel air being pushed back out of the intake and the turbo's sound to be spooling. also the boost gauge jumps about very quickly. there are no codes in the ecu and once it has done this for about 1min or so it is perfectly fine, runs sweet and boosts really well. also, while it is doing it if i pick the revs up to about 2k its sticks there for a couple of seconds and the starts doing it again. any suggestions?