There is a Wood chuck in the wood pile here
If he were driving thru the converter with a given gear, then his MPH would not have diminished with higher numerical ratios and his rpm would have to increase at the finish line and through out the pass,.......... unless the car was not moving and you were doing a stall test.
I got a feeling that we do not have all the information we need to accurately diagnose this persons car set up problems or problem.
I would suggest that this guy talk this over with Steve Schmidt further and see if something else in the engine combination is relenting or unhappy with the new port job?
Best of luck solving you issue
Bruce