I assumed emissions for petrol engines mentioned in above document refer to testing under closed loop fuel control where the pre CAT O2 sensor(s) keep ideal stoichiometric ratio of air to fuel via injector opening times. I also thought this was already tested at MOT.
I would imagine therefore any tuning via ECU re-mapping wouldn't be affected since such would only come into play during open loop conditions triggered at startup, heavy acceleration etc., when O2 sensor(s) are ignored and fueling is controlled by ECU map.
