I'am new to this site but I need some help with a 350 vortec, when I give it the gas slow everything fine but if you mass it it will stall and then pop back out the exhaust, and when its cold cranking it will pop or like run backward then crank right up, could it be the ignition switch or power valve in the holley, I have replace the distributor with a MSD HEI,adjusted the valves, timing set at 10 with advance at off, adjusted the carb idle mixter screws to get the highes vacuum,new wires & plugs, check for intake leak cant fine nothing, I am out of ideals, could used some help, thanks