only under boost, at 14 pounds its awesome all the way to redline. Above that 16, 18, 20 pounds its sputters, but will clear out from time to time. I've gone through several sets of plugs, leaned, richened, retarted advanced spark. The wideband reads about 10.5 at wide open, then when it sputters it jumps around to about 12.5. So maybe (1) of my fuel pumps is going?? I'm looking at getting an Aeromotive a1000 pump, and replace the stock, and holly that I have now.