Thanks Campgems. I agree that I'm looking for the ability to swing a larger prop, and although I didn't realize 4 strokes had quicker throttle response, it sounds highly desirable as well. I notice that on my 46AX, that before going vertical I have to hit the throttle pretty early.

However, from reading above, the 55AX sounds like it might be a better option for the Pulse. People have been suggesting the .46AX, or maybe even the 55AX. It sounds like I would need an .82 4 stroke to match the power, and that's a lot more engine than I was planning on for my second plane ($300+) The 55AX can swing a larger prop than the 46, a little more power, and won't sacrifice too much of the top end speed. What I (think) I'm going for is high speed and good aerobatic capability, not really 3-D.

There are not a lot of OS engines at my field. Other than one 46FSi on a Nexstar select, I have the 46AX in my trainer. There are lots of Magnum 4 strokes, and some Saitos. I have, by far, the easiest starting and most reliable engine at the field, and want to stick with OS. The Magnum does seem to be a performer, and the price is great for the 4 stroke, but OS has got me with this amazing new 46AX. Maybe with tax returns next year I'll get a plane set up with a nice 4 stroke O.S.

Thanks for the help.