I've finally come back to stage 4 grinding after playing on and off the past year. I've found that using gear gacha all the time actually seems to be slower than trying to get the rocket boost back as fast as possible in most cases.

There was some trouble with the first two routes giving me trouble with the AI cars.

If you don't watch the full run, I feel like Route 4+6 MUST be watched. I would consider Route 4 near perfect and Route 6 about 90% since I lucked out with contacts and with the final turn going into the next route, you can maintain the rocket boost by turning JUST on the right pixel it seems. I have done it a few times before but I've only been able to get it maybe 5 times out of 100 runs.

Route 1 - 1'00"93 Route 3 - 0'58"78 Route 4 - 0'54"04 Route 6 - 0'50"46 Route 9 - 0'51"01