i have no personal experience with m5 but from what ive read m5 has a topend lubricant and other additives that make it harder to burn. it just doesnt work well in 2 strokes. m5 will be really lean if your jetted for m1.
a post from titanracing on planetsand: "it is Nitro methane( or at least it has a 5% nitro methane sticker in the label on the drum ) along with some other compounds, I bought a drum to test and ended up giving most of it away to a foul stroke racer. the only way I could get the burn duration down was with more acetone, and prope. I believe the top-end lube was the factor that made it so tough to burn. if the gasses leave the chamber and enter the pipe burning , the whole characteristics of the pipe are altered and the rpm range will be changed drastically, I encountered bad bogging and lack of torque to the extent of .2 at the track,due to the raised core pipe temp from the slower combustion propagation, now if i changed the pipe core temp(new pipes ) and added timing and compression, I could have changed some of that but , to much to deal with and not a viable power adder just to change your fuel"