Did you have the gas pedal to the floor??? I have the MSD DIS-4 and if I put the pedal to the floor with the two step activated the motor pops (backfires).I believe I was around 8-10psi but I wasn't paying real close attention. That was on E85, 120lb injectors, PT72 turbo.
So I can't go more than 3/4 pedal. It would sure be nice to be able to floor it with the two step activated without popping!