Engine warms up and runs good. two or three stop lights and it is still Idling in drive good. turn a sharp corner and then something happens- at very low rpm (1000 - 1500) feels like a 4cyl. and then the very next stop light the egine stalls. Let the electric fuel pump run a few seconds before cutting the truck back on....crank it up and everything is fine. Also there is a constant skip but only between 4000 and 5000 rpms. Could this be related? Seems like I remember hearing something like this but cant remember the diagnosis. Any advice would be appreciated.

thanks in advance.

PS: Carb is a Holley 600, engine is producing no more than around 300hp.