I finally purchased an Autoprom and all the accessories to tune the L05 in my truck. The motor is stock with the exception of a K&N air filter, 3" performance cat and cat-back exhaust and a 180 degree thermostat. I had a bit of a learning curve, but successfully read my stock chip and am datalogging and emulating the $0D mask with Windows 8. So far the stock fueling tables don't seem too bad. I set stock AFR to 14.3. BLM's are mostly in the low 120's. The lowest I've seen is 117.

I've owned this truck since 1999 and I've always had to run the ignition timing about 4° retarded to keep it from pinging on 87 octane. I noticed some timing retard (mostly less than one degree) in TunerproRT during light acceleration. At WOT it's pulling out up to 4 degrees. The stock timing map provides 16 degrees (accounting for the 10 degrees bias) at 4,000 rpm. Thus, at WOT this motor can only tolerate about 8 degrees total timing at 4,000 rpm and 0 degrees at 2,000 rpm.

I have disabled the WOT delay and set PE AFR to 12.5. I also set all the PE added spark to zero. It goes into PE right away and the narrow band 02 reads about 880 mv. I think it's plenty rich.

For a sanity check, I reduced the bias to 6 degrees, which increased the timing map 4 degrees across the board. The knock sensor began pulling timing everywhere, even under light acceleration.

I've read various reports online that these TBI motors with swirlport heads will tolerate 25 to 30 degrees of WOT ignition advance. The motor has 160k miles and seems to run reasonably well. It will get about 17 mpg unloaded on the highway. Any idea what's going on here?