What are your minimum revs?
Seeing as you're running an X30 play around with the needles and if nothing else chuck some extra teeth on it
About 5000 from memory
When i did run restricted medium on a rotax evo i had it at 89 teeth ( if my memory is correct), but that's drastically different to an X30, so where you're at in terms of gearing and for restricted light seems about right, could be in the kart setup or in your driving, i mean I've only been to Oakleigh once with the restricted setup ( was also my first time out there https://www.youtube.com/watch?v=_nmLZqlfhKE ) and i found that you really had to nurse the rev's and be really smooth on the wheel to be sure that the rear end was sliding as little as possible. Not to assume or be rude but what I've noticed with a lot of new racers/ drivers is they have a tendency of out braking themselves into corners causing them to lose all momentum mid to exist which affects the revs drastically, and corner exist speed, i suffered from the same habit when i first started out and started to adopt the "slow in fast out" strategy. If you want to talk about it further be free to give me a call or text on 0421 494 427
I do think think the carb settings are wrong, it runs great. What sprockets do you run?
I'm running an 83t in medium, so anywhere around 81t should be ok