i have some very interesting info related to performance. Ive recently put a 400 in one of my Chryslers. i tuned the engine with the hood off. i had no pinging running 38 degrees of total timing. once i finished i put the hood on. drove about 15 min and it was pinging like crazy. i had to retard timing 6 degrees to eliminate the pinging. all this from the change in under hood air temps. coolant temp was between 180-190 for both drives. im not in need of advice as much as just curious of anyone's ideas story's or experience with this problem.