1st up get it off the hot intake, especailly if you are using a factory iron unit. Next go get a vacuum gauge. Turn your screws in all the way then back them out 1 1/4 turn, Hook up the vacuum gauge and adjust for the best vacuum reading. Then reset your idle. Now take a timing light and set your timing. A mild 383 will probably like 36-38* at 2400rpm. See if that fixes your problem.