Sorry for the late replies, I was racing yesterday (they bumped the race to Sunday), and having to keep track of my 5-year-old between rounds.
The RP gauge piggybacks on the factory sensor (through the electrical connector). With 20000+ psi, we didn't want to have people trying to tap in another sensor! It works fine with boxes which "fake out" the ECM, as long as you put our harness closest to the sensor.
The Exhaust Backpressure sensor just needs to stay below 275°F at all times, which typically requires a 12" or longer length of copper tubing between it and the exhaust manifold. You can also tee off of a factory exhaust backpressure sensor tube. We were a little worried about the soot, but we have had them in some beta tester trucks for 10's of thousands of miles without issues.
Thanks,
Michael Pliska