I have the same symptoms and code 52, short or open circuit on knock sensor. But mine is more intermittent, is it possible that it's something to do with the EGR? I can see some of my vacuum hoses are flapping in the breeze and I think some of the EGR hoses are blocked off.

Just thought I post an update on this issue. Well I got the new ATS knock sensor and installed it. Cleared the code and set the boost to max 15psi... Issue was some what resolved but still had hesitation but would occur if I push it hard... Checked the code again and this time it was 32 which was the AFM... Big thanks to Carmikey for selling me the AFM and posting out so quickly. Installed it and now the car is smooth as a babies bum... loving life again :)