God, this reminds me so much of S.F. Rush, I was driving around looking for keys for about an hour...
Some comments:
-"ESP" and "4WD" don't seem to do anything. With 4WD engaged, the truck still struggles and spins only the rear wheels when coming away from a stop.
-I think it's a bit weird that I can hit 130 (mph?) on the highway in a pickup truck and 150 in a twin-turbocharged monster. I would limit the trucks top out at 90-110 for realism and make the sports car at least a bit faster
-I really, really, really wish there were engine and tire noises. If you plan to implement a car with a 4-cylinder engine, I could even help record some of the sounds if you want (this game has me /that/ psyched)
-You should put some sort of collectibles in there and make a parking garage I can drive to the top of for awesome jumps... Or ignore this nostalgic, S.F. Rush-loving fool. That's definitely a viable option, too.
All the same, all my 5 R belong to this! I can't wait for the next build.