I've been playing this recently too and can't get anywhere near my original time and struggled on a few other games too. I've eventually worked out my issue though. I bought my driving MAME set-up from a member on here - I'm very pleased with it still and play it very often. However, on certain games I have little or no throttle response (it's either on or off without or very little graduation in the throttle). I also have a massive dead zone on the wheel which is tricky to negotiate. I set my initial time on a different set-up where things were different so sadly I can't challenge the score any more even though I'd like to. I can't seem to make any adjustments on this because I can't access various things to make adjustments. I watched the video and despite you bumping into a few bikes I can't match the time, even with no collisions (errors) - the set up just isn't refined enough.
There's also differences in the game play - Sega Rally is noticeably different, Wec-le-mans is another (it's harder to play in MAME than the actual game I play at arcade club - timer is off and the car loses traction far easier).