Thougt I'd just revisit this thread just to say where I'd got with it.
Yep it had nothing to do with the valve springs, that was just clutching at straws!
I decided to try and modify what I had, to work with an oem maf housing. I got hold of one from a B7 A4 tfsi, this is round and fits onto the itg turbo inlet pipe. I then bought an 80mm to 90mm silicone hose to connect back up to the rest of the intake kit.
So how does it fair now?
Well midrange it really takes off but top end was still struggling. After taking the filter out of the housing, I found it to be caked up in allsorts of crud.
Having no cleaner/re-oil, I just gave it a quick wipe off and it's almost flowing the same as the panel filter now but with more get up and go lower down.
The other thing is the long term fuel trim, it's sat at 5.5!
I would say that is a result