K i got my b16a2 in my car. I got a hp header for like 70 bucks. When i'm driving i can hear air out of my engine bay. I'm thinking there is an exhaust leak. I went to auto zone to go buy a better gasket. The stock gasket is really super thin and flemsy. When i went back home to go put on the gasket it wouldn't fit for ****. This new gasket was for a 99-00 civic si b16a motor.

What are some things i can do to fix this problem?
Am i losing any performance from this problem?
Is there a performance gasket i replace for these flemsy gaskets?
Or should i buy a new header? I'm thinking a greddy header, and will this come with a header gasket?

-Thanks