Well guys i have been having a knock (pinging) issue with my truck for a while now and have been going though the steps to figure it out and get it fixed. first of all i thought the truck might be running to hot so i swicthed out to a 180 stat and that did not help. so i lowered the temp setting on my fan still nothing. I even added a fuel system cleaner to two tanks of fuel, still pinging. So i pulled the perfomance tune out and reset the computer and took it out dirving and it quit pinging. I reloaded the 91 tune and it stated pinging again right away. I called superships and after some talking back and forth they seem to think that my tuner got out of calibration(did not know that could happen). So I have sent it back to them and should have it back in a week or so, i hope this cures the problem.