Markrosson

Help please ive got a 2007 a4 2.0tdi bpw engine code. couple of weeks ago the cam decided to go (rattling and compression coming back through airbox) so I finally go around to putting a new cam in it. Now I've finished the job it’s got no power till the revs go over 1500rpm. Once the turbo kicks in it drives fine, but under 1500rpm it’s dead flat. There’s no codes in the ecu and I’ve double checked all connections. I’ve tried disconnecting the mad and n75 valve and no difference, I fact disconnecting the n75 made it worse. Has anyone come across anything like this or can shed any light on this? Thanks