Pud, is it really a good idea to plug the EGR valve? It must perform a function which means there would be other side effects, surely?
It reduces NoX emissions on part-throttle by feeding approx 10% of the exhaust gasses back into the engine, and re-burning those NoX to turn them into less harmful gasses. You'll still pass an MOT emissions test with it plugged as NoX isn't tested, only CO, HC and lambda.
I understand and wondered about the sticking vanes thing, is it a big job to pull the turbo apart to check/clean?
Depends if you need the car every day, if you have a good week or so where you don't need the car and you have a good bit of free time you can do most jobs.
I don't really understand the relationship between the ECU and the 'Map', are they separate entities that talk to each other, or is the Map inside the ECU?
Depends what you mean by 'map', do you mean the map as in the ignition/fuelling/timing program that Red Dot put on your ECU? If so, this is in your ECU. If by 'map' you mean MAP Sensor, this is the Manifold Absolute Pressure sensor and resides in the inlet manifold, and provides voltage between 0 and 5 to the ECU, by measuring boost pressures up to 2 Bar (I think, or it may be 2.5 bar). If the boost pressure goes over this, the ECU gets more than 5 volts and has a fit.
Don't know if they can change the threshold for the error to be generated too, that's something you'll have to talk to Red Dot about, those computerised remapping software thingymajigs are pretty clever.
No, its not re-programmable, you could change the sensor to a different one, so it provided less volts at a set boost level, but you would have to re-adjust the fuelling map (increase fuelling) otherwise you would be running leaner as the engine would be thinking it is getting less boost than it really is.