I run the Tower Muffler on 2 OS46FXs, works great with about 600 rpm improvement but tried the TM on an AX and did not get much difference from the stock muffler with baffle removed. Either way you have to retune for this change of less pressure-richen low end and readjust high end -the AX seems to like the P-Box muffler. Also broke in and tuned an AX for a friend and came up with the same results.