Your doing the correct thing in asking for help on your car, determining who is helping and who is B.S. ing you is the hard part
Have you tried different starting line stall speeds and different shift RPM for both 1st and 2nd gear yet? Probably not yet but put that on your list to try, do one change or test at a time and keep notes for every run with any or no changes.
If it goes way slower or quicker on one run and then goes back to normal throw that run out and try and find out what happen with that run to try and identify the problem, spinning, miss the shift RPM, bogged, time slip error or what ever it was
Keep us in the loop, when can you race your car again?
