There is a lot of tuned cars here in Sweden. It is cars from 2001 and upwards that have more regulations about tuning. It's not many people that care about thou =).
The car inspection is called "besiktning".
This is my car and it clears the "besiktning" without any problems.
You need to choose the right "besiktnings" station if you have a tuned car. The people who inspect the cars can have a good day and be nice =). A big plus is if they like cars. Like the one that inspected my car this year. It was on a small station in a small city. He said he really liked my car and was thinking about getting a Impreza himself =). The car cleared the inspection without any problems.
But if you tune the engine with a big turbo etc it will be much harder. The laws says you can only increase the power with 10% =).
The most important things is that the car is safe(brakes,critical pars being rust-damaged etc) and have emission values within the limits. It the car is safe and in general good condition it will almost pass every time even if its tuned.
There is also a lot of events here in sweden. Trackdays etc.
Here you got some of my movies from different events around Sweden:
Here you got some Speedhunters blog posts about swedish cars.