I have a 04 Evo VIII, I just bought it. It had a header and turbo back exhaust. I have a exhaust smell at high boost. No smell at normal to low boost where should I start. I've looked where the boost gauge is ran through the firewall seems to be no air leak there

I have a 97 GSX w a t66 and the waste gate just dumps to atmosphere, the smell is similar to that

 

Double check your exhaust manifold for blown out gasket or leaks. The smell is a lead in the engine bay somewhere.

 

I have the same exhaust smell problem under boost. My shop showed me that I have a cracked donut gasket. I have not fixed mine yet