[2.4TSE]

My wife's C30 T5 went in for rectification of a trouble code that I can't remember but which turned out to be caused by a torn diaphragm in the PCV chamber. This was fixed by replacing the diaphragm, physically getting to which entailed removing pipes that includes part of the induction system. Also changed before realising that it was a torn diaphragm was the MAF sensor.

After repair, the code was gone - but replaced by code 640D and an engine down on power. This code indicates 'Turbocharger (TC) Control System, Signal Too LOW' and arises when the ratio between the boost pressure measured before the throttle and that which is calculated after the throttle is incorrect.

The mechanic replaced the boost pressure sensor at the end of the intercooler and this code went away.

It was replaced by 640C, 'Turbocharger (TC) Control System, Signal Too HIGH' - so the opposite of before and indicative of a boost leak. I asked that the TCV be replaced anyway as it was the original at over 150,000 miles, but error code 640C remains.

Is the cause likely disturbed pipework as a result of the other work, or something else, please? I am trying to arrange a smoke test to look for a leak that way but so far both me and the mechanic have been unsuccessful at finding someone locally enough (I don't want to drive the car for miles and miles in its current state).

Cheers!