Joel It works great!!
I have a 2004 K1200GT with a Two Bros Exhaust.
I don't think that the bike ever quite ran correctly with the Two Bros until I installed the Ztech chip.
The bike had a rough idle, could be hard to start on cool mornings, and would blow some black smoke on hard accellerations. Once I put the Ztech chip in the bike it started running MINT! Feels like it has more power too.
I think that the bike runs too rich with just the Two Bros exhaust. It can't compensate for the lack of backpressure in the pipe.
Ztech says that their chip corrects the air/fuel mixture due to the lack of backpressure in the pipe. I totally believe that. The bike now runs PERFECTLY. I love it!
I also know someone that is very happy with the chip and a Staintune exhaust.
They say that the Rhinewest chip works better with a stock exhaust but also will work with an aftermarket exhaust. I don't know, that sounds strange to me. They also say that you can just bolt on the Two Bros exhaust but in my opinion the bike didn't run correctly until I put in the Ztech chip.
One important thing to note. Ztech lists the chip for the 2001 and up bikes. Some say it is 8/99 and up bikes. I don't know what year bike you have but be carefull because there were some year 2000 bikes that were "gray area" bikes and may or may not work with the chip. I think you're safe with 2001 and up bikes.