Thanks matmatician, Felix made me aware of the meet. I will try but things are really busy here. I would so love to actually experience a well set-up car and tune. And take notes.
1turbofocus, that clears up alot. My wifes '89 240 would fuel cut at anything above 1200. It was kind of abrupt in traffic sometimes, kind of an on/off switch at times, but easy to drive around it 99.8% of the time.
As for the a/f at cruise, I understand some mfrs have done this in the past to improve mileage. Chevy used to do this on foreign market ecu's and is/was latent in domestic ecu's. Hondas VX motors went super lean in lean burn mode at low load and rpm which correspond with most highway driving and only one intake valve operation for high swirl. Not sure what lean ratios the D23 will handle well at light loads, you have a much better handle on this than I do.
Lycoming recommended down to as far as 22:1 at WOT high altitude cruise for fuel efficeincy. This resulted in low EGT's after passing through the spike in richer mixtures - but that is a whole 'nother can o' worms (little transitional response needed, constant load, very cold IAT, etc).
My driving cycle will be commuting and an occasional rip through the gears. I may do stock or ST autocross, limiting mods. The future commute will be a combo of a very short hop to a vanpool site or an 80mph 75mile drive one way. Temps will be between 28F and 125F. Will have to pass Calif smog inspections with little effort.
So I'm trying to make this decision: Just get a PCM update (last one was in late '05) at the Ford dealer at about $100 hoping it will clear up the driveability issue and increase MPG. Or get a tuner and hope the $400 will clean up the driveability, add MPG and be able to reset to stock to pass smog tests.
How would you spend your money?