Body removal from chassis

What would happen if you bought a car from the US that has been modified, or had a 800 up engine in the stock chassie?

How do they know how much HP your engine makes? How often do they test / check, you could build what you want from a stock looking perspective and swap out the engine to a stock engine for testing etc.

You need to move to a non socialist / progressive country. What's next they take your guns, oh wait they already did that.

I glad I'm in my late 50s, I don't have too many years left to have to deal with this BS here in the US when it comes here.