I still think it shouldn't affect power. Remember, the dyno is ONLY measuring torque and figures out HP from that. Since it sees how fast the motor is moving compared to how fast the rollers are moving, then it automatically knows what gear ratio you have in the car and thus should be able to calculate accordingly. We tried to dyno my friends El Camino, and it kept stopping the run because it was all screwed up by his stall converter (motor revved real high then wheels started to catch up).