SBC idle problems need help
Hello all, I have a SBC 350 with a Carter 625 Carb new, great compresion 175-180 on all 8. Replace the distributer 2 times with new Accell coil cap for HEI 2 times, plugs, wires, cap, Rotor, This is my problem the engine has less than 10k on it and I was driving it after a tune and it had great power and then just started stumbling below 15000RPM just no power sounds like it not running on all 8 or exhaust is pinched. It is firing great on all 8. The only thing I changed was I pluged a vacume port on the carb that was not previously pluged. I have tried everything, it is getting really bad gas milelage and is low on power. I also just adjusted the valves today. Any help would be great I am stumped. Thanks to everyone in advance. I am so lost on this one. The engine is a 1978 4bolt main.