What are some things to look for to get rid of my REAL knock retard??? I just put some 100 octane fuel in the car and the knock retard went away.

Here is what my plan is...tell me what you think!!

1) Get some GM Top Engine cleaner and clean all of the carbon out of the cylinders.

2) I am using a factory heat range plug, but I am going to switch to a colder spark plug just to try it out.

Any other ideas??? I just hope I won't have to tear the head off of it to find a hot spot.

Thanks