We drive our L78 Chevelle (factory 11-1 spec.) quite a bit (32K miles over the last ten years). By jetting a little rich and playing with the advance curve, ours runs just fine on 91-93 unleaded. High octane gas needs lots of compression for it to ignite properly. It needs the compression heat. A lower compression engine running 112 octane gas, isn't going to run as well as if it was running 91. You see low compression stock cars running the high octane stuff then wonder why their whole exhaust system is red hot. Much of the gas is burning out there instead of in the combustion chamber. Retarded timing will have them glowing too. Get your fuel, timing, and jetting right and you don't need header wrap. I don't. Race specs and street specs shouldn't be confused. Tuning on a chassis dyno will do wonders for most cars. A wide band O2 sensor is a good investment too. It will probably pay for itself in gas savings alone.