For the drift stunts, just make sure you keep sweving back and forth and try to hit the road signs. Each one gives you a .1 adder to your multiplier.
Also if you have a near miss with oncoming traffic that's another .1
My best combo is over 26k.
I've got 100% complete and still don't have my last barn find.
1 or 2 more nights and I may have all your records smashed!