I fly a 3d profile with a OS 55AX. I only got a 600rpm increase using a Jett / Evolution performance exhaust over the stock muffler with baffle removed. APC 12x4 13,900 vs 14,500 rpm. I heard that stock the Evolution 60NX has a throttle transition delay which makes the engine junk for 3d, however several people with the performance tuned exhaust said the engine was transformed.

So does this engine transition a lot quicker with the Jett clone muffler? Good enough for 3d? Can it be modified for a front needle valve, does this help?