Would definately not be "Overpowered".
With the current air accelerate you probably wont be able to get 800-900 (Cars can go much faster and provide alot more acceleration too! )velocity due to the way the map is made, you simply can't turn fast enough without losing speed. (Running is 240 velocity, max engine speed is 3500).
It also balances the issue of players who can bhop easily getting away from the cops right now and would make cops vs raiders much more fun and interesting.
In terms of raiding it would be pretty much useless in case you're worried about that other than escaping.
The only issue I can think of would be using ramps to slope off.
would bring balancing, more interesting gameplay and general fun without ruining any current gameplay as far as I can see