Modifying cars in Finland

[TheTurbedKiwi]

I'm a huge fan of Japanese cars, asolutely obsessed. I understand there are Japanese cars in finland, of course, but they are fairly expensive. Compared to the prices I might see in here in NZ, but I would be far more interested in knowing more about modifying cars.
I believe there is a form of "carbon tax" on finnish vehicles? Can car modifications affect this tax say if I improved the efficiency of the engine? Would the age of the car affect that?

Is the addition of Turbos, Springs, chassis/sway bars and roll cages etc. allowed, forbidden or extremely expensive?
What can you and what can't you do? Estimation of prices?

Assuming there are finns in Finland I would say the rules are very serious and not to be taken lightly

[Upphew]

I believe there is a form of "carbon tax" on finnish vehicles? Can car modifications affect this tax say if I improved the efficiency of the engine?

It is measured as CO2/km... so it isn't just that you poke a probe to exhaust and get nice reading. The measurement will cost 2500€ at VTT.

[Kartell]

Basically, for every mod you do you need to have TUV papers and have it registered. Cars are tested by autokatsastus every year and if you dob't have the paperwork for your mods you don't pass.

I do however see a bunch of modded Skylines, Silvias and Imprezas around Vantaa and there was a big surge in RHD jap import some years ago. Not sure how these guys get around the katsastus coz I'm sure they all have illegal mods.

[Upphew]

Not sure how these guys get around the katsastus coz I'm sure they all have illegal mods.

A bit of elbow grease before the inspection I suppose.