So my recent new toy went into the local garage to have a look at a few of the 'issues' its got, one of which was a bit of a blow from the front end somewhere on the exhaust. When i went back in to get the car he said ' did i want a seat b4 he told me the problem!' (Never a good sign!!) Anyhow, he says that one of the 4 cats has a crack in and replacement part is Ł700 odd They said there is the possibility of having it welded as its cracked and not rusted through but what i was wondering is, can i bypass these cats with a full system (milltek or similar) or will these need to remain in place for MOT's etc??

Cheers in advance