Got a mk1 vrs and bought it with suspected turbo fault but once I looked into it boost pipe was gone way beyond belief, so changed that and the car drove better but was like the engine was in limp mode. (Turbo sounded okay and no damage or play) so connected it up to my friends vagcom which fetched up two codes one was egr valve (short to ground) and intake flap (short to ground). I then began to look and realised that it was running an N75 which I believed to have been mapped in, anyway I changed the plug for one of the two that was left dangling down and it got rid of egr valve code but fetched up a boost sensor code. Now I know it’s the n75 causing this issue but am I better finding a new vac box and pipes, or sorting the mess of a n75 out? If finding a new vac box where can I get one as local to north wales as possible thank you. 

The N75 valve isn't necessarily faulty, it could have been really badly mapped and the MAP sensor is picking up overboost and the ECU is putting it into limp mode, or it hasn't been mapped and some muppet has fiddled with the stop screw trying to get more boost that way with the same result.