im totally against octane boosters....yes they do foul plugs prolly due to an additive in the booster and they also eat away at the oily film that is on the cylnders which over time will cause more damage if used prolong times...if you are going to do anything run your tank down then fill up with higher octane and enter your tune...i dont really agree with these companies having a true 93 octane tune because of so many different locations and air differences in the locations....My last race engine was 12:1 compression and ran perfect after tunning on 93 octane