wonder if anyone can help me please I have a vw touran sport is it the pd engine I've been told 05 plate . It started running lumpy so the aa came out and without checking anything he said it was a burnt valve ??? Then another garage told me it's the injector seals ??? Then I've not been convinced I've look up YouTube etc about checking the air mass sensor so I brought a new one fitted it and it seems like the mass sensor isn't doing a thing same symptoms plugged and unplugged is there a fuse to this ?

There is no fuse for the sensor

Sometimes if there is an issue with the MAF and you unplug and it runs better (default running setting) then it proves the MAF is faulty.
If it made no difference when it was unplugged then chances are its fine

Do a scan of the ECU fault code memory to see what codes are stored in there (if any)
Beyond that then proper diagnosis of the engine is required

Thanks for your reply