Up until very recently EPA-traktors were exempt from the yearly mandatory vehicle inspections of cars. This meant all controls were "in the field" where discovering the various changes can be hard.

It has been somewhat of a sport to find new sneaky ways to make the cars go fast and/or quickly lock and unlock the car with a hidden lever.

And most of the cars are in rural areas with little police presence. Outside of urban areas sweden is very sparsely populated. My parents live out in bum-fudge nowhere with something like 2 people per square km. Up there every other 15 year old has an EPA-traktor.