u7153 still pinging on 91

[bshort]

After a smog, I re-installed the tune in my 01 f150 screw 4x4 5.4l. I'm running 91 Shell and noticed pinging just before the wot shifts. I retarded 10% and still pinging, although a little less. If I go to 15%, this would be the same as the 87 recommendations. I don't want to retard so far that I would be killing any chance at gains. Any recommendations?

[mikel]

Sounds like it could be a spark issue or even a clogged fuel filter. Also try different brands of gasoline as well.

Thanks

[bshort]

Fuel filter is fairly recent, no issues with plugs or c.o.p.'s. I do not race the truck, just occasionally romp on it to merge. My #1 reason for the tuner install was to recalibrate for gears and tires. Q #1) What is an acceptable amount of retard? Q #2) How much can I retard before I go lower than the stock curve? Q #3) Will adding X amount of fuel at 4-7K table help to keep the ping down? If so, how much? No dynos even remotely close for proper tuning... Please advise.