Can you use the stock gastet that goes to the precat with a downpipe? I think I remember reading somewhere that you can, but I wanted to make sure.

 

Indeed you can. Just make sure it is not all fugged up.

 

Might as well replace it with a new one unless yours is in really good shape. They are kind of expensive though.

 

I reused mine. The gasket set I bought from Malloy didn't come w/ that.
Just clean it thoroughly. Laquer thinner works great.

 

They cost an arm and a leg from Mazda. If it isn't damaged then reuse it.

 

I replaced mine for the hell of it when I swapped motors. Seems the downpipe gasket was reasonable; it was the two between the turbos and exhaust manifold that were like $70!

Unless it's truly mangled don't worry about it though.