well, my motor when i got it i was told it was a 383stroker motor...but i am not positive...would there be a way to find out for sure w/o pulling the motor apart???? when i got the truck, it had half a tank of feul in it...i then filled it up with cheapo(87) and drove home...no biggie, it wasn't till the next tank(100% 87 octane) that it began to diesel, and run funny...well, today at the speed shop i asked the guy what he thought and said, you may need to run premium feul, so i just put 20bucks in her(from empty) and ill see how it runs. another thing is that i bumped the timing 2 degrees(to 10 DTDC) last night to see what would happen...should i back it back down???? basically, how do i know if i need premium...should i check the compression???? any help is appreciated. oh yeah, it also idles funny...if i tap the gas, it will idle down to around 500(where i have it set) but i have to hit the gas pedal once or twice to get it down there if im going from drive to reverse/vice versa or if i just started it. sometimes it will get as high as 8 or 900RPM's....would that have to do with this????? THANKS!!!!