Hi Bertie,
I would always go remap over a plug in box unless it's a new car under warranty
as the Tmc box can be unplugged and is therefore untraceable,also you could
Sell it on after a few years and still recoup at least 50% of your outlay.
I had an Angle Tuning remap done 8 months ago and the car has not missed a beat!
I'd definitely recommend them,Rob is the man to go to.
If you need any more info please Pm me as I've had lots of work(and more to come
next month)done by them and I'm 100% happy with the service/results.