I either have jinxed motor or extremely bad luck trying to run my Perry 550 with a 2100cc engine. I had the 2100 in before with twin 40 webers but it ran ragged, it idled rough and wouldn't smooth out until I hit 3500 rpms. I dropped a couple of big one and some change at the local flat-four shop but it only ran well for a couple of days. I dropped it and put my 1680 back in using the same webers with which it ran like a dream. This time I reinstalled the 2100 with a single 44 weber and it idles better but when I accelerate hard it boggs down, backfires through the exhaust and I can hear the the weber sputtering. I have an electric pump with the fuel pressure guage dialed into 3psi. I have a single pipe quiet muffler installed as I don't want to lose any more hearing. I followed most of the suggestions in my Dellorto tuning book (similar types) except for chaging the jets, on one hand they say increase them and the next time they suggest decreasing them. Since I don't have any spare jets laying around, any suggestions to point me in the right directions? Oh ya, please no crude remarks about my mutant Perry 550, I like it and only wish I could afford to build a Beck or other more exotic model.