Scott,
If you're running a header, I would tend to agree with the double gasket routine. I think there is a great expansion/contaction issue with a header vs. the stock cast manifolds. I have the Gruppe-S GT knockoff header...sitting on a shelf right now. I had a miserable time trying to seal it up, then when I got it pretty well set, I simply didn't like the loss of low-end that the header produced. So back to the stock manifolds. Maybe when I get stupid and go Satge 4+ I'll put the header back on, but for now the stock manifolds do fine.
I do think you get a bit of noise off the wastegate that sounds much like a leak. Can't tell for sure though. There are advantages to getting older and deteriorating hearing
Plus my car came with a seriously upgraded sound sytem.
I'm done at the office now, so I gotta go do the Dad thing with the kids. Let me know if the gasket stuff works out.
Take care,
Kev