I've got a 97 3.4 T-100 w/ 96k and when I bought it it pinged even on premium. I ran seafoam threw it in the intake and as a gas additive on two occasions with no effect. I replaced the plugs with the ones recomended for the supercharger application (colder) now it runs on premium and only pings on hot days under heavy load or with the A/C on. If I use 89 it pings constantly when put under load between 2200 & 3000. I don't want to run on premium I'm cheep and premium isn't! What do I try next? I was tempted to replace the ox sensor but thats an expensive shot in the dark. <img src="/forums/images/graemlins/confused.gif" alt="" />