Just fitted some new piper anti pump lifters. they have been in 2 weeks and have started to tap.

i have spoke to piper and they said its very rare to have faulty ones, but have sent me 2 new ones that i have got to swap around and try. but he said before i do that it could be the oil pressure.

some kind of ball on the distributor side of the cam may have come loose apparently. anyone know anything about this?