Manufactures employ the use of a cat to lower emissions to pass its tests, so by removing it should usually fail thus creating high emissions being vented into the atmosphere which is very much frowned upon by environmentalists. If it doesn't pass the legislation expect to be ordered for a retest MOT or fined by police.
For whatever reasons Toyota put two cat converters on (maybe for emissions legislation in Japan ) the car only needs one after 31 July 1995 to pass emissions and none to pass the Non cat test before 31 July 1995. Regardless if your tester is friendly or not, once your car details are entered he can do F all about the emission results as its all registered on computer, Unless he doesn't notice you reverse another car in when he goes to the toilet.
This is where a friendly tester comes in:
Loudness of an exhaust should not be louder than a standard car, this can be overlooked.
Smoke can also be overlooked.
Everything you need to know is in the link below.
In-service exhaust emission standards for road vehicles: 17th edition