Thanks for the input, and yes, tis been a few months of this then that, starting with a new engine harness, which was "all it needs". NOT! Sorry, perhaps not quick.
Dave Barton's Dutch-sourced harness and support is awesome and reasonably priced, but after it was in, the car wouldn't start. Fuel pumps ran, but I found no spark at plugs. With guidance mostly from the FAQs, I changed the ignition module on the L inner underhood wall. Nope.
No fire from coil, so after two other coils and a complete bypass of any car control of it, a new coil got spark to the cap, but nothing out to the wires, despite those new cap/rotor parts. Plug wires looked excellent but new cap/rotor did the trick to start the car, but I found the warmed-up power to be dismal, with all other driving aspects quite good, IF seemingly low on boost and low vacuum.
Cooled turbo showed easy spinning and no detectable play.
The pro who knows this 765T said the AAM was dying, 'cause the engine quit when it was unplugged, despite voltage variance with varied airflow as I revved the engine. The replacement changed the running characteristics, but did not solve any other issues. He got it to backfire, which blew the brake booster elbow apart. That part was changed.
Only very minor vacuum leaks fixed after a pricey smoke check. Also fan clutch was reported weak. After a very warm indication a few days later, a new tropical Aisen went in. The car stills runs just above 1/2 gauge, but there is no more coolant loss.
R&R of intercooler and thorough degrease and flush removed very little crud, similar to what I found in an earlier boost hoses look for oil. Still no detectable boost escaping from those hoses which appear intact and firmly clamped.
Adjusted the wastegate arm, both ways, with no betterment in boost. Reviewing the old school vacuum troubleshooting chart had me check ignition timing, which seemed close to spec. Rotation to max, improved acceleration and vacuum with no pinging or knock. That sensor tested high resistance, and was cleaned prior to reinstall.
A pretest for smog, indicated the Calif, sticker, and probably a bad cat. As earlier stated, it rattled when slapped and a flashlight revealed comb material had partially melted and was mostly lying in pieces inside the housing, all removed, but that explained the normal temperature rise between its in/out pipes. There was some catalyst operation, but not enough to pass muster. I was unwilling to drill test holes fore/aft of the cat for pressure differential check.
The car drives quite well, otherwise. The amateur/hack aftermarket radio install by the PO is now done properly and the replacement "proper" Chinese power antenna does NOT fit a wagon, despite all eBay listings' assertions. I repaired someone's erroneous wiring of that switch and circuit and plan a new flat antenna.
Many red plastic interior parts fixed or replaced; power seat operation fixed.
I think the center driveshaft support has too much play; on the to-do list./ Also on that list is a proper redo of some vacuum lines, particularly the HVAC feed, which is now tied into the 1/2" hose between IAC and vac pump, leaving a capped intake port (noticed by the smog tech). There is a small leak somewhere in that circuit, either cruise control or underdash pedal 'switch' or HVAC actuator.
Mulling the value of ipd's (on sale) F/R sway bars, recalling the driving joy of an earlier 245 brick, so fitted.
Have no cat; will shop!