I tried some M3 when it 1st come out along with a new engine that I did not have a handle on the tune up at the time,it made no different.But they say the M3 is for the carbs. & M5 for injection,and to be honest I do not think I riched it up enough.I was getting my info from a chevy guy,and Mopars seem to like more fuel than a chevy.This time on the dyno now that I know its richer (almost listen to some more wrong advice or misunderstood what he was saying)if I do not see anything going 8 steps richer(meaning use a smaller jet in the return to richen)I will try 12-16 steps richer.

"Good Luck" Guys trying the M5,hopefully in a few weeks I will have some dyno results to share on switching from M1-M5.

PS It might not be a bad idea to try a small timing change,to get better results.