Alright, so I've lived with it on the road for a few days now, and yesterday was a pretty hot day (hot for me: approaching 30*C) and I could really feel it start to hesitate as if it were pulling timing or something. I built a diagnostic tool as per the instructions on Swedishbricks (except I didn't have a 560 ohm resistor so I used a 510 - I'm sure this doesn't matter) and installed it. This morning was much cooler, maybe 15*, and I didn't feel any running issues but I did observe a couple of brief flashes. It didn't happen all the time, and it didn't seem to be specific to load (though it was more common at higher loads) nor did it seem to happen specifically at 2000 RPM +/-. I'll observe it for a few more days and we'll see if I can establish a pattern.
Part of the running problem is likely from the different injectors I used - I used a set from a B6304F - they're rated the same flow but they operate at different pressures. My wideband didn't show anything untoward at WOT but there might be some differences because I'm having some funny starting issues when both the weather and the engine is very hot. It fires instantly and then dies, and then requires a couple seconds of cranking before it fires up again. I'm running a brand new fuel pressure regulator and a brand new fuel pump check valve, so I SHOULD be maintaining pressure at the rail. It certainly starts better than it did last year, before I installed those parts, but by the same token I don't have any frame of reference because I've always been dealing with a different hot start problem until now, nor do I have a frame of reference for what WOT AFRs should be with stock injectors. They're showing low 12:1 now, a bit richer than I'd like but not as rich as I'd expect the factory to be.
I read that you B280E guys got different ECUs, and I don't remember if I read that you got different ICUs but you may have.
On a different topic: you folks considering building headers for these engines, either size them "too big" (i.e., 1.5" OD or larger), make them unequal length, or prepare for a lot of noise. With the exhaust I originally built, the noise was obscene. I have since swapped the rear muffler for a large Dynomax oval and an S shaped tailpipe, and it's quieted down a lot, but I've still got a loud resonance at 2400-3000 RPM, where the pipes come into play. The 1.375" equal length tubes make pulses so powerful, it's just RAPPPPPP... Otherwise it sounds pretty good. Hell, it even sounds alright in that area, it's just not what I'm looking for (unless I could make that noise from 4000-6000 RPM, tubes much shorter than 33.5" would be needed, possibly unequal length to extend the range.) And with the automatic, it ALWAYS seems to be in the 2400-3000 RPM range.
