I am convinced that most stations here in Birmingham...probably the Southeast, are diluting their 93. I have my TLplus WOT spark timing set to 6. That should yield 3.3, 6.6 and 10 deg of timing pull up the rpm band. Nice power robbing setting. But today, which was cold, it pinged with almost any boost after a few gallons of BP. You guys have recommended Mobile, and shure enough , that has been the best gas so far with almost 0 Knock, except for a few times wide open. My boost winds up at 18psi. I busted a station here a few years ago after my GTO motor pinged like a field of cicadas. They had 88.7 in the 93 spigot. (got the weights/measures guy out there). I am going to call our new and lame weights/measures guy and prhaps a TV crew. I have called him when i got a tank of seriously pinging gas, but no call back. Today, i got some gas that was as bad. The only other thing, I do have a set of heads that i paid to have ported by a guy on this board, I got some other heads back, (mine were un-touched) that were cut so much that intake barely fit. I always say, the GN really needed a few more cubes so we can turn the wick down alittle.