In Road Trip Adventure, there is a way to get Devil Parts, which are the best in the game. You can only get them for Tyres, Spokes, Engine and Meter though. Go to Cloud Hill and find the Rainbow Jump. Outisde that house, next to a lamppost, should be a car. Talk to him, and he will ask you to collect 100 stamps (he will also give you a fake God's Rod, which goes in your garage). Once you have collected all 100 stamps, talk to him and he will give you:

Devil Tyres (best Tyres in-game!)

666 Spokes (don't really do anything, they just look cool)

Devil Engine (reaches a speed of 349 in about 3 seconds from standing. Also jumps straight to Reverse, even when at top speed)

Devil Meter (like the spokes, does nothing, but looks cool)