Cheapest easiest fix it to run 85% corn fuel (E-85) you will make more power and contrary to the guys bashing it on here it help control detonation NOT cause detonation. There are lots of guys running 15 or 16 to one on e-85 with no problem. When I am in OK city visiting my folks I use it in my cars, it is every where down there. I ran it all the time in Tennessee and I wish it was available here. It also carrys more oxygen with it so you can richen up the mix and make more power with no engine mods nessacary so it is way cheaper than tearing you engine apart and replaceing heads and pistons.