were you retarding the timing when squeezing the juice? You should be retarding about 2* for every 100hp of shot???
Tuning with fuel pressure will negate itself as the computer will compensate in other ways. It is a band aid fix.
we had premium in the tank and by inspection of the plugs, no discoloration of the ground strap suggests no detonation was going on. There weren't any specks on the porcelel. We put in plugs 2 steps colder and it worked well, but SLOW