Hi there I am going to change the cat on my st170 just woundered if changing it to an after market one would this make the engine light come on thanks.

 

It shouldn't do but you can clear it easily with an EML code reader.

 

stay with the standard ford ones mate changing them on a ST170 wont give you any more power be wasting you money

 

A standard for cat ford st170 is £1170 whereas a sports cat is only £400, even if it makes no extra power, it still makes more sense to go for the aftermarket cat

 

Doesn't the ST170 have a sports cat as standard?

 

It has 300 cell or something as standard, and aftermarket has 200, won't make much noticeable difference, but as it's nearly a third of the price to a standard cat it makes sense to go aftermarket if it needs changing.