Originally Posted by jeweler54
Also a rich air/fuel ratio will INCREASE knock . . . i found that out on my mustang.
Thats actually the opposite. A leaner A/F ratio is more apt to pre-ignite.
Matt, what your describing is carbon buildup and/or a lack of adequate octane for the timing of the tunes.
To prove this.. run the tank low and then fill up with some 92-93 octane. Then put in your 87 tune and keep bumping the timing up til it knocks.
If it doesn't then put in the 93 tune and back the timing down until it does'nt knock. This will give you a basis as to what things allow for more timing.
IMO you problem is most likely carbon build up. A good sea foam treatment and a good quality fuel injector cleaner will probably fix the situation. (I'd suggest chevron with "techron" cleaner)