The standard header bolts are not long enough, especially for the TTI thicker flanges.

I used longer bolts than the 7/8" long standard bolts. You can get longer header bolts than what is commonly available and that helps keep them tight. Mine have been in since 2007 when I replaced the motor and I have not touched them since.

My collector gaskets are the same ones that TTI supplied and have been in service since 1999 when I installed them and they don't leak.