i have a w reg 2l and that only has 1 sensor, the later cars came with 2. the second is purely there to check the function of the cat so make sure you use the first sensor/wiring harness as its this one that used to control your engine. i would have thought thered be 2 bosses for sensors in the system unless the second sensor is further down in the flexi section?? EDIT: and then you just run an lambda/O2 sensor cheater which is a little plug and play wiring harness that fools the car into thinking its got a cat on it and so doesnt put the mil light on!

with regardss to fitment if its like my focus central 4-2-1 it replaces the standard manifold and front mounted cat and bolts directly to the standard flexi section. cat back systems seem to be from the flexi back though which is weird but it works well as mine goes like stink and i got pretty much 150bhp in march on rr with milltek cat back, focus central 4-2-1, pannel filter and uprated cold air feed to air box and my flexi is a replacement from motorfactors and i think its a narrower bore than fords so if i find a bigger one somewhere i'll prob fit that as i recon its the only restriction left