There are multiple threads regarding high compression...
Do you know what detonation is?
Detonation is what happens when the fuel doesn't get ignited at the right time.
Maybe, the longer exhaust duration would help, but that is throwing away power and money.
I've heard of people using a hotter spark (i.e. MSD ignition 6AL box) to make sure that all of your fuel is burnt at the right time.
Then again, maybe the higher octane in Tennessee will be the answer to your problem.
Also, running a richer mixture might help but that make your engine dirty.
Hell, I've asked many questions; posted, searched and PM'ed until my questions were answered and I probably annoyed the hell out of some people with everything.
Not trying to sound rude but I've gone through similar stuff
http://forums.hybridz.org/index.php/topic/105053-high-compression-questions/