Waldo, its the 70 magnum. I figured it would pull it around just fine as well, but so far, the vertical isnt real great. Not sure if its the altitude or not. I bought a 14x4 to try on it to see if it works better. It wouldnt hang on the 13x6. I started with a MAS 13x6 and went to an APC. The APC was better. I could hear the MAS vibrating the crap out of the plane. Nice and smooth with the APC. I just got it broke in, so maybe its just not at its peak yet, I dont know. Im still having fun with it, but really wanted some vertical pull out of it. I adjusted the valves and checked the valve springs, as they are know to be kind of weak. The both feel fine to me. I did put the tach on it and it was spinning mid to low 9000's. If it doesnt improve, I may have to contact magnum and see what the scoop is. It should turn around 11000 or so. We will see what happens. My mustang PTS with the 46 evo has better vertical if that says anything. Its turning an 11x6.