Not running right on part throttle?
 

Car does not start right away, takes three turns of the key. Then takes at least ten minutes to warm up. Also car only runs nice under full throttle. Back fires through air box and will only stop back firing if given full throttle. Car is a 1978 sc with 964 cams. No smog! I have tried playing with mixture and have only made things worse. I think it is running too ruck but cannot be sure! WHere do I go from here?

I mean too rich.

I would check the fuel pressures. It could be your WUR