my friend has a carribean 19' with a 454 bb and jacuzzi. motor is mostly stock with a mild cam. we broke in the cam at 2200 rpm and then took it 4 a test run at lake elsinore. made it 3 laps around before it started backfireing out of the carb and losing rpm n power. we replaced the gm hei cap and rotor for a tried and true accel cap, coil, and rotor. when we launched at the river(lost lake) it ran great for a half mile up river before the same problem returned. by the way, he is not much of a lead foot, more of a cruising guy. i appreciate any help.