That was maybe too short of an answer. I had the same problem. I Changed jets and needles till I was sick of rejetting. The problem only moved up and down the rpm range. After unplugging the tps the rev limiter went back to normal operation. I can hit it as hard as I please an it will just cut back normally. NO complete shutoff as you are experiencing. The tps particually on the speedmasters seems to cause this for some reason. Performance will otherwise not be affected.
