Don't know if its the timing or what but it runs really good but when i barley move timing its sluggish and won't start. had to stop because my neighbors are pissed. so i don't know if timing was the problem... can't work on it anymore tonight. I ran it for 2 weeks with straight headers. no muffler or cat. It has a muffler on it now tho.still loud. Motor is modified and throttle body injected around 350-375 hp. 400 with a higher psi regulator(maybe). Has about 12 degrees of advance on the balancer. where is ballpark good timing on a hp 355? has 10:1 comp, 272 dur. 447 lift cam,holley pro-jection manifold, 670 cfm tbi, camel hump heads, flowtech headers and y-pipe, k&n , 3" exhaust, and 45 psi fuel pump with a 22 psi fuel pressure regulator. Holley makes a replacement 35-60 psi for $50. I don't think the stock fuel map would affect the idle but it will need a custom chip when it's on the road. Only thing not hooked up is the knock sensor... still waitin for a welder.