Vintage Cars: 1976 Mercedes 450SL - wont start, but runs with gas in ignition and full trottle

Question
Hi guys

I got a weird issue with my 1976 - 450SL.
Bought the car, has been sitting in a garage for a couple yrs, looks awesome, 130K miles.
Had it trucked home, replaced fuel pump, fuel filter, couple fuel hoses, drained the tank, fresh gas, new spark plugs, checked electricity, etc etc etc.
Can 't find the standard full pomp relay/breaker in the trunk by the way???
Cleaned several switches, checked vacuum lines, vacuum hoses. They all seem to be ok.
Also cleaned return fuel line, fuel lines to the injectors.
Even checked the WUR, looks like new inside.
Car starts but stalls within the first one to two seconds, fuel pressure seems to be ok, pump runs, got fuel to the injectors, got pressure on injectors, air filter ok, settings (air/idle) is ok I think (turned it 2.5 turns counter clock wise after turning it all the way in).
Got a good fresh battery, but the car won't start. It 's not that I don 't know anything about cars, but this one drives me nuts. Previous owner had a mechanic look at it and he could not figure it out.
He replaced the fuel filter and stuff, but that 's all I know.
Found out that when the wife starts the car, and I poor gas in the intake, and manually hit the throttle that I can start it up, very rough for the first seconds but suddenly it started!!!!
But I had to keep the RPM 's high enough to let keep it running. I had it running for over 5-7 minutes like that, temperature was ok and yes it sound 'ok', I could even hit the throttle a couple times and it picked right up. As soon as I released the throttle to let it idle (throttle close to the intake manifold), the engine died again and now back to the first issue, can 't get it to start again. Not even with new gas in the intake like I did before.
It really looks like it dies right after starting it, over and over again. Same thing, like somebody pulls a plug when it starts….
Fuel pump works perfect, I hear it, even when I unplug the plug on the intake manifold, than it runs smooth….

Answer
K jet - correct?  your year is inbetween a Kjet and D jet system
seems like you have checked the systems that I would check, however i think your issue is in the Aux air valve,  it is a classic symptom and I think it is sticking .
have you checked the cold start injector and thermal time circuit associated with that injector?

if you send me an email address I can send you a trouble shooting guide for the Kjet