Programmable ECU's and closed loop lamba control

[Supercharged]

I was just wondering if anyone on here owns or has any experience of a catalytic convertor equipped road car with a fully reprogramable ECU that will easily meet MOT emission tests?

I was wondering about this because I've heard that it is extremely difficult (read expensive) to map them for proper closed loop idle control that is necessary for a modern cat equipped car to consistantly pass a emission tests.

As far as I understand it when the engine is idling the fuelling, ignition, and stepper motor are all constantly being varied to keep the rpm within a certain set idle range while at the same time the signal from the lambda probe is used to alter the fuelling to keep the exhaust emissions in effect 'clean'. Plus to make things slighly more complicated you've got the added problem of fluctuations in the rpm due to a varying loads on the alternator. Which all means that mapping it correctly is a very long process.


Well I've rambled on a bit, but basically what I want to know is if I fit a programmable ECU to my car will it be possible to map it (without costing thousands of £'s) so that it will consistenly passes emission tests?