I havn't had a chance to run my bat pipe on my ET engine. I have run it on a JPX .21 in an X2 CRT. This was on a mid to large size track ( MotoRama ) and the engine has maybe a Gal on it so far. The bottom felt good, not too snappy but strong. The mid range was insane! The pipe really felt like it was holding the engine back, on top though. Now, this may be due more to me needing to break in the engine...but it just didn't feel right on top. I will give it more time though. My local track is supposed to be opening this w/end. I will say this, if you decide to try the 2013 exhaust, both engines are animals. I run weekly on a mid size track and can avg 8 mins of runtime.
As for the ET, while I loved the way mine felt with the 13, I eventually settled on the 2057. Slightly softer on the bottom, slightly more RPM range on top, and I could avg 9:15 easily. I also plan to try the bat pipe, ie- 2056-, on the ET and will post later.