I dont know if you have solved your issue but....
97 to 99 audis do not use MAP sensor. AEB engine codes only use the N75 valve for boost control. The N75 valve is located at the turbo inlet pipe. You definately need to tune you car if you want to got wide open throttle with it. a K04 is slightly bigger than a k03, therefore flowing more air throughout the rpm range....at 5k rpm its where it could hit overboost and cut you off.
The moioaning could be your turbo going bad...did you buy it new or used? thats how mine sounded with the the turbo took a dump on me.
Do you have the CEL on? if so have it scanned at autozone for free and get back to us here.
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98 Audi A4 built 1.9 gt30r SOLD
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Last edited by pipe7284; Jun 3, 2011 at 04:26 AM.