Just ran through the first race at Trial Mountain, you're not allowed to tune the car in any way save for adjusting some of the Driver Aids (not ideal, but ok..), biggest thing to note is that Skid Recovery Force is forced ON. This IMO is a bad idea, it basically made this race stupidly easy to the point that even with my wild "it's AI so I don't care" driving style, numerous bad corners / wall slams and almost rolling the car at least once on that last corner thing I still managed to finish 10 seconds ahead of the 2nd place car.
If I was actually trying to drive well I'd imagine I'd have been another 5-10 seconds further ahead on top of that, I just checked the final Suzuka race for the special outfit and it's the same.. Skid Recovery Force ON, don't have time to run it right now but unless the 1st place car starts stupidly far in front (which it might) it'll likely be too easy. I'd have thought for the special prize like that that it would be harder (i.e. no SRF) so maybe it's an error on PD's part jamming that aid on, I don't know.
I will say this though, I did enjoy blasting around Trial Mountain in a Nascar so it's a shame there's no repeat prize / incentive to redo the races. Even if after you receive the initial big prize + ticket the rewards switch to basic seasonal payouts like 300k and a helmet / suit for 1st place that'd be more than enough incentive, at least for me, to rerun them a few times.