hi looking to fit a exhaust to my car have been told that fitting the whole system(backbox, centre and downpipe) will put the engine management on even when fitted with a sports cat. anyone know if this is true or had the problem?

 

I have fitted a complete system including sports CAT from H&S and I have had no problem.

 

I think there may be problems with CEL lights with a decat on newer cars with the air pump, but the ROM can be edited to stop this.

 

As above, a CEl fix is available. Aren't you worried about your warranty ?