The future of engine tuning

[Roadrunner]

I've heard a few comments that some engine tuning will possibly fail your car come mot time, as the manufactures quoted emmission figures will not be a match anymore. Also something else to the effect of using anything other than the standard engine management system / engine will become an automatic failure, also due to matching up part numbers or something.

All this technology seems to be keeping engine tuners in tight check. So is there any possibiliy anymore for engine swops? For example, some guy's put an exige or bike engine in a lotus elise etc. If some of you out there are working on a project like this does it mean you will have major problems in the future? I remember reading my Dad's Street Machine magazines as a kid. It was full of crazy engine swops and only restricted by the builders imagination, not EU rules. I don't see any harm in an engine that has safe emissions that just happens to be used in a different vehicle than intended.

Can anyone clear up my confusion over this?

[Tuff Noodell]

I would have thought that there is still scope for conversions/modifications using the Single Vehicle Approval route. SVA allows emissions to suit the age of the vehicle/engine as I understand it.
I dont know whether this can be applied to cars that have been already registered.