454 exhaust gasket - what works????

[Jim85IROC]

My exhaust manifold gasket developed a nasty leak this fall. I finally got fed up, and rather than screw with it for an entire weekend, I sent it to my trusty mechanic, who put in a new Napa exhaust manifold gasket. Nice and quiet. For a month. Now it's leaking again. I've got the other gasket, but I don't really see much point in going through all that work to get another month out of it.

A buddy of mine suggested a copper manifold gasket. They seem to work well with headers, but I've never talked to somebody that's used them with stock manifolds. Is a copper gasket going to be an improvement over a stock style, or is there something better out there?

This is a 100% stock tbi 454 except that it's got dual exhaust. It still has the stock manifolds though.

Thanks.