How do i get emissions down on 1995 mk3 1.3 fiesta

hi, i have a 1.3 fiesta mistral and i cannot get it to pass mot on emissions. Ive done the basic stuff like oil service, new air filter, new fuel filter, cleaned spark plugs and set gaps, checked and cleaned electrical connectors

Ive put on a new catalytic convertor and new lambda sensor

The engine was breathing real heavy and wasnt running right so put another engine in.

When i rev the engine up it burbles for a bit before speeding up. I think the mixtures wrong, and its over fuelling. Its not adjustable either so its all down to the engine management.

Anyone got any ideas?

Go to Auto Zone or Advanced Auto and have them pull the codes. This will give a place to start. Try cleaning the Maf sensor.