In reply to Mikedsilva,
Yes, cat bypass with all three configs. My 964 came with a cat bypass and I've never seen the need to remove it, especially since emissions laws in MA were changed a while ago to not require emissions testing on cars 1995 and older.
Comment to Justin's last post:
When I used the cup pipe + secondary muffler, i could not for the !@#$%^& life of me get rid of what I'll call a "whine" or "squeal" at around 2500rpm, +/- ~500rpm.
I had that witch apart countless times, tightened everything, loosened everything, installed new "donuts", took new donuts out and greased them, etc., all to no avail. so now it's G-pipe for me. Swan pipe does the same thing, just provides mounting arms, IIRC.
Pretty much ticked me off, since I did like the sound, but driving around town, as you well know, is usually in lower rpms range.
I am curious to know if any other cup pipe users had a similar experience and, if so, how did you solve it?
TIA, as always, for your help.
Phil