Keithr726

Your diverter valve should not be making that noise, that shows its bad. Running a blow off valve will give you the loud wooossh but it will cause your car to run rich. My evolution motor sport billet diverter valve i got from lindsey works great and makes a ppssshhht noise but its not really loud but I can still hear it with my windows down.

The original ones fail often. In fact they don't even make them anymore and you must get a new 993tt one to keep it stock. Don't buy ebay crap, get one of these instead...

http://www.lindseyracing.com/mm5/mer...de=BYPASSVALVE

Naplesguy06

lindsey offers two types in billet. 1.Bypass valve non diaphram(99-0609-00) 2. Adjustable Biller (BOV cm) which one is correct ?