It shouldn't do - cat removal is a fail, because it interferes with the emissions on a petrol engine. From the MOT manual Section 7.4 on the VOSA website:
Reason for Rejection
1. The exhaust emits dense blue or clearly visible black smoke for a period of 5 seconds at idle
2. The exhaust emits dense blue or clearly visible black smoke during acceleration which would obscure the view of other road users
Note: The criterion is density and not volume of smoke. The description ‘dense smoke’ includes smoke or vapour which largely obscures vision.
A well maintained engine shouldn't produce anywhere near that quanity of smoke.