"BAD" --

Well, I'm glad it's solved.

As far as the rich running is concerned, likely culprits are the TPS, CTS (too high a resistance or a bad connection), CSV (possibly stuck open, even if not connected), molested or damaged AFM, resistors added in series with the CTS and buried in the wiring harness (e.g. like on my car), FPR (regulating too high)

PS I enjoyed your photography. Seems we have more in common than a love of often cantankerous Z cars: www.graphic-fusion.com

Thanks!

TPS: Inspected with cover off, seems to be working fine. Tests OK at ECU connector.

CTS: Replaced. Tests OK at ECU connector for the given temperatures.

CSV: Replaced. Verified that it is not stuck open when not connected.

AFM: Replaced. Rebuilt unit from MSA.

CTS wiring: ECU connector tests don't suggest any problems. Haven't ripped the wiring apart to see if anything has been added, but it doesn't look like it's been touched in the past.

FPR: Tested fuel pressure at rail and verified 35psi

It's running a bit better than before as I think some of the carbon buildup has burned off.

Well, the vacuum reading and the plug reads are the final tests of how your engine is running. On a well worn engine with good compression (like mine), engine vacuum at idle should be 18-18.5 in Hg. An ideal reading would be maybe 19. A marginally acceptable reading might be 17. This mostly tells you how good your mix is at idle, although larger deviations from this mark would also indicate something about mixture under load. There's a mixture adjustment screw at the base of the AFM near its outlet, concealed beneath a small plug. It doesn't really do much on my AFM, but it might on yours. Clockwise would be richer and CCW leaner.

Then your sparkplugs are the ultimate reading on mixture. Run your car around for a while, and pull them. They should have a nice mocha coloration on the insulators. White would be too lean, and black would be too rich.