Depending on what stage map you are running, you could have anywhere from 30-60ft/pounds extra at the wheels, so yes that could be it if the clutch was going.
But what your describing doesn't really sound like a slipping clutch to me. A slipping clutch will be more noticable in the higher gears -it gets worse with each higher gear, you'll see your RPM's going up w/o a matching increase in speed. What you were seeing sounds more like a fueling glitch. Reflash it again and see what happens.