98 GT pinging

[CADreamin]

I have a 98 GT that's stock with 60,000 miles. Only modification (small) is a K&N filter. For a while now, the car pings when under heavy acceleration or going up a hill.

Just drained, flushed, and refilled the cooling system. It is in good working order with no leaks. The thermostat and fan work as they should. I sprayed the wires on the MAF (which had some crud buildup) with electrical contact cleaner. This has helped the problem and the overall running of my car, but has not eliminated it completely.

If it stops raining long enough this weekend, I have new plugs, wires, and filters ready to go in the car. I do not have a timing adjuster on the car and assume the timing is stock, though I have not checked it.

Any suggestions from the group? Is a good tune up likely to take care of the problem? Or could it be the EGR valve, carbon buildup, etc? Is there a good way to de-carbon a 4.6L without pulling the heads?

Your ideas and suggestions are appreciated...

Thanks,