I have my car set to where it runs awesome at idle and while driving, but when I come to a stop it starts to run rough and the rpms drop to like 500 and it acts like it wants to stall. I do notice that my brake pedal feels hard when this starts to happen. Is this because of a vaccum leak or because the motor isn't making enough vaccum?

I have a 350 with 416 heads, edelbrock 600cfm, holley mechanical pump, comp 270 h-10, holley street dominator intake.

Any suggestions? thanks

 

Probably vacuum leaks, or you need to tune the engine, carb, and choke.