Hi . Just a quick one . Before forking out on getting vcds reading I thought I'd try you lovely people . 2.0tdi 170 has destroyed 2 egr valves. And throws p0406 sensor a too high . When maf is unplugged it runs fine without p0406. When maf is plugged (also tried a new maf) the revs become eratic and throws p2108 throttle body.. also loud clicking coming from egr throttle body area when car is turned off after drive. Any pointers would be much appreciated as It's just failed it's test because of eml being on . Sozz if this has been covered before .. ps the previous owner for some ridiculous reason put an induction kit on it .. so no original air box.. any pointers appreciated.  Thanks 

Hi I would find the wiring to the egr and follow it through the loom back to the ecu and track for any shorts to power, seems like you have a chafed loom somewhere and the egr is getting too much voltage i.e from another power source along that loom.

Easiest way to check is get a multimeter and set to volts. Unplug the egr,  Black onto an earth point or battery negative and probe each pin until you find battery voltage or 5v reference. If either of these are an odd voltage like 8 or 9v when they should be 12v or 5v then you definitely have a short to power.

If you find that you do, overlay a fresh wire from the correct coloured wire or pin on the ecu straight to the egr, just to prove the repair would work, run the car and see if it's cured and clear the codes. 

If all is well then back to tracing the chafed loom for a proper repair. 

Should do the trick, if not give me a shout! no problem. 

Thanks very much for the advice . I shall have a look this avo .. fingers crossed ..