Exhaust Manifold with Sports Cat

Just had some work carried out with KTEC this week which they found out the my exhaust manifold is blowing. Looking at Renault parts they are way too expensive so need some advice where or not this would be too loud when motorway travelling but also whether or not the car would pass the MOT with the delete of the pre cat and change to a sports cat. (Already got a Cobra Cat Back System)

Changing to:
KTEC exhaust manifold
Cobra Sports Cat
KTEC Induction kit
RS Tuning Re Map
 
I have the ktec manifold, sports cat and exhaust on mine and it's pretty loud on the motorway although my car is stripped which obviously adds to the noise. I think you'd be fine with the MOT.