Aftermarket can and K&N fitted, not fuelling properly - help!

[Dead Eye]

You dont need to narrow anything down --- just put some gaffer tape over those holes

This is what I would do as my first go to option - its cheap and will confirm whether you've accidentally messed up the air flow as so far its the only "non-standard" mod you've done. As noggy pointed out, the majority on here run with a free flowing air-filter (typically K&N) and an aftermarket exhaust without any issues.

If you still have a problem then try to switch back to the original filter (if you still have it) and the OEM exhaust after as well.

Finally, its back to basics; check air, fuel and spark