since the other user hasnt answered, might i suggest the trail mountain cup?
many users are grinding this race for credits, and the tomahawk s seems to be the fastest car available for it. the best ive done with my limited tuning knowledge is a ~1m34s lap on the reverse track, and i feel like there is certainly a lot of room for improvement with the car that is beyond my knowledge and understanding. id be curious to see how fast it could go with a better tuned suspension and gearbox