I am using a 3" ATR downpipe with external wastegate.
a turbo to downpipe gasket causes the wastegate not to seat?? hmmm never heard of that in my life. been runnin one for YEARS. and its ok if its leaks? yea, then condensation from when you first start the car, runs out of that joint like a FAUCET. im not sure how a ball/socket type joint would seal without a gasket there. and yea, it wont actually hurt performance, but itll be a tad louder, and leak all the time. not sure how desireable that would be.... i bought mine at murrays for 5 bucks. dont have the part number though. i could get it for you though.
if you have the stock style waste gate you should not use a gasket there. It won't hurt performance if the flange leaks there. If you install a gasket it could make the WG puck not seat flush on the turbo housing causing a leak. this will hurt performance, cause slow spool etc.
I have a brand new ATR copper gasket. Jace, will a tracing or a photocopy help?
Mark
Seturbo makes this ATR ext wastegaste gasket you need. I bought two of them at the Southeast musclecar national in Reynolds Ga in November. I am not sure if they have them listed on there website. Give them a call.