Just got a focus st170 as a daily driver, took it for mot and was told the cat is goosed but it did pass but sounds like its breaking up Internally, was told to buy a decat as the cheapest option but my question is do i have to heat wrap it or can i leave it bare ?

 

If you fit a decat it should fail its next MOT under 'catalytic converter not fitted'

 

funny enough I asked a mate the same question today and was told wrapping it cant hurt but you dont have to, and mine still passed the emissions test too

 

in the end I wrapped mine and would advise if you have not done yours to do the same as it really does keep the heat away from the sump big time

 

just remove the cat and break the innards out and then re fit it

 

Only issue with that is the terrible tinny sound the exhaust makes and the cat is not very free flowing due to cats shape

 

I have a 2003 focus st170 and I just put on a stainless steel manifold and a sports cat and just left the rest of the exhaust the original. I heat wrapped the manifold and It does feal alot more racier but the heatwrap does stink as its burning in.If I can get the hang of uploading photos I will show a few.