That sure sounds like detonation to me, don't try WOT.

What heat range are the plugs? Maybe go one colder? I agree the plugs look lean but could also be the heat range. Let us know what you find out.

I had similar problem/sound on 89 3.2. Also had SW chip. It was a 24 pin rebuilt ecu. I sent it out and had it gone through and 28 pin stock chip installed. Cured the problem. No more pinging.

So we swapped in a known good AFM and no dice. Ignition timing was also checked and shows normal (atleast at idle). So we are learning towards that not being the issue either.

I swapped in a stock chip and the problem goes away! Puzzling. I had some thoughts, perhaps the wrong map is on the chip or maybe there is something mechanically that is 'borderline' and it is exaggerated by the chip.

Anyhow the engineer in me is still not satisfied, so i will perform some other testing by checking AFR with both chips.. hope to get that done tomorrow. This will atleast verify if it is indeed fuel related or something else. Hopefully will have the chip sent back to 911Chips before the weekend to verify the maps on it are correct for my car as well.

If you hear the issue at idle I find it highly unlikely it's chip related, you can't really mess things up that bad at very light loads like idle. You did report the issue even at idle are you certain it goes away with the stock chip? or could it be intermittent issue? Do check AFRs but I doubt they change much between stock and SW chip.

EDIT: I reread your first post, issue seems to be only at higher loads, AFR test is the next step. I'm betting you will find your lean at hi-load to WOT loads. You CAN NOT be above 13.0 AFR at WOT anything above that is simply to lean. And a SW chip if run lean would cause issues as would any perf chip running 30deg or more of ignition. The stock chip runs no more than 27deg so it can tolerate the lean conditions a bit more than the perf chips could. AFR testing is the next best step.

Just to followup on this, but i finally figured out the issue.

So as it turns out the car was running super lean, i hooked up a wideband O2 and was surprised to see it almost 1 full point lean under all running conditions. With direction from Sal, i tested everything on the car and all showed normal with the exception of a misadjusted full throttle switch. I tried to tweak the mixture using the CO adjustment on the AFM. This helped at idle but made no appreciable change under running conditions as expected.

At this point i was out of ideas and decided to check the clock spring on the AFM. I noticed what appeared to be a scribe mark on the clock spring that was about 7 teeth in the rich direction. I decided to try adjusting the clock spring back to where the scribe mark was. The car now runs significantly better and the AFR's are normal under all conditions now. I tweaked the CO adjustment with the help of the wideband and also reset the idle speed.

At first glance my AFM appeared to have never been opened, but I cant say for certain. I figure at some point this car was probably running rich, and to fix this issue the clock spring was adjusted in the lean direction. I did not check the AFR with the AFM my mechanic swapped on, but we dont know the history on this one either so who knows what kind of tweaks were ever made to it.

Appreciate all of the feed back and a big thanks to Sal for all of the help he provided me.