Mechanic advice/expertise please

[MattMF1]

my car has recently developed a tappet/value lifter noise under acceleration. The car is a MkV Golf 1.6 FSI if that helps. It seems most prominant in 2nd and 3rd gear but non existant in 1st, 4th, 5th, 6th. If i accelerate hard in 6th it doesnt do it, in second and third however, there is a clicking, tappety noise. Any ideas?

Thanks for any responses

[MattMF1]

You cant really hear anything tappety on idle, it only seems to be on acceleration