I have a 1971 240z, when I bought it it ran well and was good all summer and come winter time I had some minor things to fix. Decided to pull the engine and rebuild it. Everything was cleaned and put back together, everything seemed fine but now it won't start. At first there were electrical issues, no power to the ignition. That was fixed and we tried to start the car. With the throttle fully open it will turn over really rough but it runs, barely.. it sits at 1000rpm and after a couple minutes it dies (that is worth the throttle fully open the whole time). We checked compression it's good, checked for leaks at all flanges and there are none, replaced spark plugs as 3 were shot, firing order is all correct, it's a twin carb set up and we checked both float pots on the carbs both are getting/have gas so It is getting fuel, if you release the pedal it dies instantly. I have no idea what could be wrong.. has anyone had the same issue? Or any ideas on how to fix it?