Induction kit running issue

[discomark10]

Hi guys,
I installed an iduction kit to replace the standard air box today.
It started fine, idle seemed ok, but when I took it for a test drive it was very slugish and sort of bogged down a low/med revs. Seemed to run a bit better with higher up the revs.
I ended up putting it back to standard shortly after as I needed to use it and it ran fine so the maf must be ok.

Any idea's why it ran like that?

Thanks