Above stuff + run a few bottles of injector cleaner in your next tank of gas you buy somewhere else. I run 87 in my V6 and only get occasional pinging on very hot days under very heavy loads. The EGR ports could be very clogged ($5) or you may need to overhaul the intake and injector harness ($60).
http://www.contour.org/mods/mods.cgi?s=howto&display=intake-overhaul Any CELs?
