Check cam timing also make the engine has a good ground as well as the chassis I have extra dyna s and dyna coils if you need some to try. Double check your battery we fought issues for 3 weeks once and we ended up having a bad battery charger. If its breaking up at 6k and soaking the plugs you could have a return line issue providing you run one. It def sounds like your running alky right through the motor and what doesn't get burned internally is burning in the header hence the flames. Hth