I found a Cheat that works I am lvl 36 in the game. I have Tier 3 GT R. I got 2 more Tier 1 car full upgrade. when I take my GT R out it kinda Sucked. So I Delete one of my Tier 1 cars and got a BMW Z4 upgraded. when I took my GT R out a few hours later it seem to Acceleration faster and handling better So I said something in game chat a few people said it's in your hand. so now I have 2 Tier2 cars in my safe house it does work.