First I have to say thanks to all of you that helped me with my 72 Challenger project. The car is pretty much complete at least I can drive it. Well I am up to the tuning phase of the project when I'm driving the car at a cruise speed about 2000 rpm the car will kind of sputter kind of like mmmmmm puh puh puh mmmmmmmmmmmmmmmmm puh puh is that from a lean condition or is it not enough timing? the motor runs fine at idle and at full throttle. The motor is a 512 with stealth alum heads Holley 950 HP, MSD pro billet dist ( still with the facory setup) and MSD 6al