740 failing smog, very rich when engine hot

I apologize if there is already a post about this but I am new and I couldn't find one. I have a 1986 740t wagon that I am trying to get passing smog. has a brand new cat, o2, and coolant temp sensor. Symptoms are passes when engine is cold at 15mph but fails 25mph. With engine warmed up fails both as gross polluter. I also tried replacing the AMM with another 007 from a junk 240 which did nothing as well as a reman from Delphi (a10335). The reman made the car idle terribly and run super rich. Any ideas that could help me out here?

edit: forgot to include it is failing for CO and HC

Have you tuned the engine up? New plugs, cap, rotor, and wires go a long way to helping a rich mixture. How was the wiring on the coolant temp sensor that was replaced? You want to measure that circuit by testing at the ecu connector for the proper impedance at temperature. Alternatively you can measure the voltage on the sensor and see that it progresses properly according the information on cleanflametrap.com.

Don't forget the air filter. A clogged air filter can make the engine mixture rich.

Seeing the actual numbers from the report (CO2, CO, HC, O2, NOx) and limits would help.
How "cold" is the engine when it passes @15MPH? They are not even supposed to test unless its at normal operating temp.

Oh yes I forgot those were the first things I went after. Changed the plugs and wires (had a miss from one wire arcing). Checked cap, rotor and air filter, they seemed fine. I did some testing after posting and I don't believe it is going into closed loop.

If it never goes into closed loop operation. That is a sure sign that the coolant temp sensor circuit is having issues. It's the most important circuit as it overrides the ecu wanting to go into closed loop. If the sensor has too high a resistance like an open or high impedance. Then you get a rich mixture all the time.

Check the fuel pressure regulator too, on the front end or the fuel rail. Pull off the vacuum hose and see/smell if there's any gas wetness in the hose or coming out of the fitting.

If the regulator's diaphragm ruptures, the regulator (a) won't close and lower the fuel pressure to where it should be under vacuum, and (b) will let raw unmetered gas get sucked through the hose into the engine. Both will make it run way too rich.

Also, if the hose itself is split or leaking, no vacuum is applied the the regulator, and it runs rich.

Ok so checked fuel pressure and it sits at 3 bar steady. I'm a service writer at a volvo shop and my 2 techs keeps saying it's the AMM. I've tried several used ones with no luck. My last chance before forking over big money for a bosch reman would be trying the one from my 88 240dl that is my daily. My boss is convinced that it's is a fault in the cts circuit and I noticed there is oil and gunk all over the wires under the intake manifold so I'm going to take the manifold off and clean up all of that today. I'm out of the shop for the weekend now though, so access to diagnostic tools is limited.

Do you know if it has the original harness or not? possible the insulation on the sensor wiring has rotted.

On my LH2.2 740 Turbo, it ended up being leaking injectors causing the rich condition.