Aftermarket [noisy] intake and exhaust systems, CO2 etc.....

[MantaRay]

As we all know, vehicle manufacturers spend millions of pounds developing their vehicles to meet all the legislation required. Given that their vehicles have to meet drive-by noise legislation and declare a particular CO2 rating, why can Joe Public purchase intake and exhaust kits, fit them, and no longer have a vehicle that meets type approval legislation? Does the vehicle then become illegal for that reason?

[woofgang]

If they become too noisy they are illegal, if the emissions go up they are illegal. They might also invalidate insurance if not declared. BUT enforcement is of course a different matter!

[Toureman]

The enforcer will step in once a year and if the emmisions are to high he will put the car off the road until it is fixed.

He is called an mot inspector.