But Mad North-Northwest
Join Date: Sep 2003
Location: SF Bay Area, CA
Yeah, the S3 has a manifold pressure sensor (behind and to the right of the passenger seat, I think.) It serves to increase the advance at cruise for better fuel economy.
Unfortunately the bellows in them tends to crack and leak, hence the whistling. It's an induction-based sensor so I don't know of any easy replacements. A lot of folks just cap off the line if it fails.
1963 Giulia Spider (1750 engine)
Former: 1987 Milano Gold