Do you have an exhaust leak between the turbo housing and header?

This Turbo to header gasket is like the Turbo Riviera gasket that everyone used until GM discontinued it.

Made from .065 thick graphite impregnated high temp material with stainless steel core.

The Turbo Riviera gasket hung in the exhaust flow and had to be trimmed carefully.

This gasket is the same size as the header so no trimming is necessary.

This gasket will take a lot of abuse.

Run a file over the header flange to see how badly the flange is warped.

The header turbo flange WILL be warped if you have used a copper gasket in the past.