After about 30 minutes dies at idle


1990 SL500
I have a 1990 SL 500 with 140k miles. The car was left sitting for 9 years (before i bought it) so I put a new fuel tank in it, new injectors, cleaned the lines, new high end radiator, new engine mounts, and performed all basic services. All instruments work and the only light on the dash is a wiper fluid light for some reason. I have driven it a few hundred miles and i have always noticed a gas/rich exhaust smell. It starts with a bit of effort when cold and needs a couple of throttle presses to start, it runs kinda loopy and sounds kinds like an old race car.

So basically It starts hard and smells rich once warmed up and then after driving for a while like 30+ minutes it will die at idle without throttle input. at stops i have taken to neutral and giving it a bit of gas up to like 1k rpm and then i shift back in to drive when its time to go. obviously something is not right and i have no idea how to tune one of these and its driving me bonkers. I am an electrician by trade so i have basic mechanical skills and solid electrical troubleshooting skills and no one i have talked to about it, even the local european only mechanics, know anything about these engines and tuning them. So i am just looking for a place to start, like i said i had the injectors pulled and replaced because it was running even worse before, so injectors should be good. Is there some kind of control and adjustment for these that i could play with to get the car from running rich. I can live with the cold start thing but the dying thing has to stop
Sounds like a lambda or air intake sensor issue to me. Read off the fault codes from the ECU hopefully it's logging something out of the ordinary that will highlight where the problem lies. AFAIL cats were fitted around this year, is it working ok? are the emissions readings within normal parameters?

Pull the spark plugs and check if they are sooty, if so it is running rich so the next step is to work out why. Does the engine temp read correctly?

Which engine does this have? the M119 came as a 4.2 5.0 and 6.0 although functionally they are all similar I'm guessing it's the 5.0.
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5.0 and as it is a 90 i don't know how to check anything with the ecu because i dont even know if it has a code port. engine temp reads between 80C and just below 100C degrees. Emissions wise where I live that isn't even a thing so i have no idea
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