Parts costs

[LuckyLu]

We should be able to keep the parts that we buy for some car because you will waste so much money testing out which setup works the best for the car. What happens to the parts when they get switched? They go right into the dump and get sold for 0 ? lol 
please implement this IM POOR.

[deadboy]

This got suggested already 7 times before, and it will be probably part of the Dyno-Update, which will come in future.