Definitely some sort of timer cheat for the Insurance Fraud...or from the other angle if not a timer cheat then a money cheat for the amount of damage done.
That's the last Activities I have to do are the blasted hard-level Insurance Frauds.
I didn't need the time cheated on the Trail Blazing...just aim for people on the sidewalks even more than cars. And once you obtain the vehicle ability to put nitrous on all vehicles that helps, too. Although maybe the vehicle already has nitrous (I got the ability before trying any Trail Blazing).
Slightly off topic, but it should help. Insurance Fraud doesn't end while you are still getting points, so all you need to do is keep falling every time you get up. I was able to make up the last 50k on a mission after the time had expired.