TOL channel 1. They've done it and channel 2 as one-off's from time to time I believe. No clue what it actually sounds like though since I have yet to play an IE4 / TOL.
It's interesting to me that it isn't offered standard in a dual like the 3/4. All of the TOL clean clips I've heard are excellent. If that is indeed what it is designed to emulate you would think it would be a standard in the MOD series.