p0340 code on my b7 a4 need some advice please

Recently had an issue with my a4 tfsi where it felt flat at low rpm and car was throwing an eml light on the dash. when the turbo spooled up power was there but not 100% so something wasnt right for sure.
I took it to my local garage who read the codes for me to diagnose the issue, it had all the codes read, it had a few they said lol.

So... the garage replaced the PCV valve and N205 valve. Car was still in some kind of limp mode after all this and clearing the codes and showed a single p0340 code with the eml light still on. At this point the garage suggested to let them go ahead and swap out the camshaft sensor which i agreed to. So they did this and cleared the codes once again and gave me the car back.
Car still feels in limp mode, no power at low rpm but with the difference that now the car feels like it has no power at all more like a non turbo fsi, no EML light on the dashboard however. Im a bit stumped, I've taken the car back to the garage and they plugged it in to a diagnostic machine and said the p0340 code is still showing which indicates camshaft sensor but still no eml on dashboard which i find odd.

Anyone have any advice on this? Maybe had something similar?

Thats a good shout actually. Wiring or plug going to the cam shaft sensor could well be at fault I guess. I have a volt meter at home, is this something i can do DIY?