Az. salvage yard?
might be your power steering or something in that nature
If you buy the vehicle with a as is sticker there is no return time-- when you cross the curb it is yours And even if you purchased it other than "as is", it would depend on what the problem is for it to be covered under warranty (which your liking it or changing your mind are probably not covered things) - and the seller generally has the right to fix the covered problem, not refund it. Essentially, a purchase agreement is an unchangeable agreement made then to purchase, for better or worse, for both parties. Consider all the reasons it is needed:, you used the car - maybe abused it, he couldn't sell it while you had it (costs to the biz in missed sales), making car sales refundable just because, would eliminate the need for the car rental industry. There is no reason you can't sell the car yourself now though.
Many cars have speed limiters or RPM limiters to protect their engines from falling apart and destroying themselves.
One can buy speed limiters that can be attached to the engine/ignition/fuel control.
By fitting a throttle restrictor. This would have to be custom made, most garages would be able to do this work.
Don't worry, they will find you. They always do. Hint! Make your payments on time and they won't be looking for your car.