73 MB 450SL stalls after warmed up and will not start

[Jonchip]

I am hoping that someone might be able to shed a a little light on my situation.
I have 73 450SL that I inherited and have been trying to get back to running condition. I am a retired Toyota tech of 23 years so theses European vehicles are kinda fun to work on. Unfortunately I am at a point of frustration right now... Let me tell you what I have done. The vehicle had been sitting for a while when I got it and did not run. I have put a new fuel pump and filter with new gas to at least get to run. I then did the normal maintenance spark plugs, wires, cap and rotor with points. After that I noticed that it had a little stumble in it so as rotted as a lot of stuff was I checked for vacuum leaks and ended up replacing all injector seals and some vacuum lines. The vehicle was and is running great! Fires right up every time.
The problem I am having now is after it sits at am idle for about 10 mins or so it starts to stumble and them stalls. It used to be that it would start after about 5 - 10 mins but now has got to be 1 - 2 hours before it will start. And sometimes longer. This is what I have done for diag when it will not start back up.
I know it is not a spark problem because it will run on alternative fuel source. I have check fuel pressures and it's at 31psi and does not bleed down for several hours. I have check the wiring to the temp sensors and ohm'd them and they seem to be good.. I pulled the trigger points and checked them and they were in great shape.. All relays are good and fuses. I put a stethoscope on the injectors when it is warm and they are not firing when trying to start it. Also when it cools down the starting injector is not kicking in (there is no power to it) but if I supply power to it the vehicle tries to start but doesn't. I am probably wrong but I keep thinking it's temp related but the funny thing is when it cools down it still will not fire up sometimes.
Any help will be more than appreciated if anyone can give me something to try next. I know it's going to be something simple in the long run..
It always is! Thanks