We tested the exhaust gaskets on a crossover pipe. If the bolts weren't tight, then the gasket would "burn up" and just leave a "skeleton" of the original gasket. If they were tightened properly, they were fine. You have to keep exhaust gaskets tight, or they will burn up and be no good.
The gasket "fried" with only 10 hours on the dyno.... :banghead:
You may want to check your gaskets to make sure that they are not already toast....