I'm thinking of getting a decat pipe for my 06 ST. I know that once it is on that the car won't pass an emissions test for the MOT. Is the pipe easily changeable? For example is it a bolt on replacement for the standard cat or is there welding involved when fitting/removing it?
What effects should I see from fitting it too? I was hoping for a bit more of a rumble from my exhaust, is that correct?

I don't think catalysts act as silencers so it should sound the same.

De-Cats are a bolt-on replacement but you will get the MIL on and the car will be running to compensate for the No.2 Hego saying that the cat is not working.

This can only be removed by having the car remapped.

I would spend the money on a manifold, exhaust and a K&N first as that will give you a better improvement.

ive got a miltek flexi and decat, and its does make a difference. you can hear the sound difference, i think its mainly from the flexi tho. does pop now.lol. some how since decating mine my mpg has gone up.lol

I am considering some exhaust mods including the de-cat pipe.

Has anyone had problems getting insurance with this mod?

Is it illegal / will it invalidate insurance?

I found a thread which posed this questions on another random forum, but it's not too conclusive...

Any ideas people?

What remap should i use after de-cat to switch off the MIL on dashboard? Is Dreamscience helpful for this?

It is both illegal and irresponsible to decat your car.

If the plod catch you and run an emissions test you will fail and be liable to put the cat back on and pay a fine and even if you don't get caught you're polluting the enviroment without need.

Regarding insurance, its a mod that you could claim, but would the insurers want to cover a car that they know to be illegal?!?

the plod aint guna look under your car, unless your exhaust is well loud, and if your taking just the cat out, it dont make it to loud. youll need either a bluefin or dreamscience to which the mil light off. or you can go to puma speed and they sell it a mil eliminator for £50, but i have been told by some people this doesnt alway work, but should do. if i didnt have my bluefin id just leave the light on, unless it bugs you.