I test drove a 02 S4 at a dealership (and a 05 too) and it made a wheezing sound for about 20 seconds. Restarted the engine and it didn't reoccurr. Is this the air injection pump? It almost sounded like a wheezing exhaust leak-- hard to describe...just didn't sound right.
Our A4 2.8 doesn't make that sound, so it's peculiar (and has the air pump).
The S4 turbo ran well, but was somewhat surprised to hear the turbo's spooling up at times, leading me to think there was some kind of minor leak.

Any comments are appreciated.

g2

 

Welcome to the forum g2!

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Which S4 was making the noise? Describe the noise differently. When exactly was it making the noise? At start-up, idle, cruising, cold run...??? And what do you mean you were, "...surprised to hear the turbo's spooling up at times."?? The turbos should always be spooling up when accelerating and you should be able to hear them always (unless a Harley is next to you).

 

My 00 S4 does not make a funny sound at startup. You can hear the turbos' spool up. They seem to be a bit louder when first started, and when being light with the throttle. But a prolonged 20sec wheezing sound does not sound right.