As for backfiring.... I could do without it. It's kinda stupid when i'm driving a BMW 5 series and all of the sudden, ..BAM.. when you downshift. If I paid $60,000 for a car and it backfired like that, I go nuts at the dealer and say I got a lemon. Backfiring on "stock" cars is totally unrealistic.
TIRE SMOKE
This is a big thing. Sitting there doing a donut. Smoke is gone in about oh, say half a second. Thats not right. lol! And I love how you go through grass and you have fluffy smoke coming out. Ok fine, fluffy after a couple seconds, but at first have it look like dirt and grass chunks are flippin' out from under your tires. I guarantee when you punch it, fluffy smoke is not gonna be flying at 3 MPH.