Thanks for your reply. The car is a '90 with 167k miles.

On the Bosch Super (copper head) plugs the car will start and run but with alot of noise. Sounds like a severe "clacking"/"knocking" coming from the rear of the engine. Once I heard all the noise, I shut the car down, put the +4s in again and she ran "normally" (normal for me). All compression readings were done with a hot engine. The 150 was measured after a can of BG44k in the tank in addition to the steam+Sea Foamcleaning method, like I said, the Bosch Super plugs worked well after this. Baffling, frustrating.

The car idles rough and shakes when warm. At speed the car runs strongly.

Ringlee's reply to my post (and yours) makes complete sense, there must be something else wrong. I think at the time I posted I was just overly frustrated with the car...now that I've come to my senses and thought about some things I don't plan on pulling the head. From my reply to ringlee's post I mentioned the TPS resistance wasn't reading properly according to the Bentley manual.

The engine management system is the LH 3.1, non-adjustable TPS. Is my TPS (and all throttle position sensors) also supposed to "click" off idle (like the 2.4 systems)? Mine doesn't. My wifes '94 940T (LH??) does.

This is my theory, I may be way off base but it's the best I can do with my limited knowledge of how the TPS/Fuel Mgmt system works:
* A normally functioning TPS = sensor resistance at "idle position" signals the Idle control valve to open and regulate the air mixture properly.

* Bad TPS = My thought is that with an abnormal (high) resistance reading at "idle position" the engine thinks that the car is off idle so it's allowing more gas and not regulating the ICV. The RPM sensor limits this extra gas since it's reading that the engine is at/around idle. Engine doesn't shake when cold. ECT resistance is at "cold" , the extra gas isn't noticed as it's acting like the cold start injector...as the car warms up and ECT resistance changes turning off the cold start injector, the engine starts seeing this extra gas (from the faulty TPS) and idle hesitation/shaking since the air+fuel mixture is off.

Does that sound reasonable? Please correct me if I'm wrong.

Timing is right on. I live in a cool weather climate, thermostat is new and cabin temp guage runs rock solid at 9:00.

The 89 octane I can say does cause knocking, just put 93 in there and still have almost a full tank. Was running 91 for a long time but honestly never noticed if it made noise (I've become very aware of the noises the car makes now).

Thanks again. I'm getting a new TPS today. Will let you know if this solves my problem (man do I hope my theory is right!)

Zuda