[Bruce Edwards]

One other question that will help make this a bit clearer at least for me. If you shut off the idle screws will the car run better or shut off? If you turn them in and the engine smooths out the idle system is dumping to much fuel. No other thing will do that short of your NOS system leaking fuel. If the engine has EVER backfired the powervalve could be bad. If the carb sat on a shelf someplace for a long time the valve could be bad. If the engine idles with the screws turn almost all the way in and the float level and bleed holes are clean it MUST be bad.