I should clarify - I was meaning only to setup the spark correction vs. coolant tables for testing, and once the optimal values were found, set the table back to original. So this way I completely bypass having to do more invasive stuff like what Robert mentioned, and instead simply setup the spark correction tables for temporary test values and add a switch and potentiometer to the ECT wiring, then return to stock when I'm done.

Mark - do you mean WOT, or part throttle? I know some guys who have added a lot more timing here and there without knock, although it was all in part throttle areas and I don't know if the tables I saw were at or beyond MBT or not. How clean were your combustion chambers when you did that?