I am pretty sure they are the same. If you search the forum that thread should eventually pop up.
In cylinder pressures during combustion should be anywhere around 1000psi (ish) detonation will double this suddenly. If the turbo is on the limit it will be pushing more heat in there which won't be helping.
Ultimately it really comes down to tuning to suit level of boost you are running relative to the quality of your fuels.
Did you mention what turbo you are using and was it making more power above 20, 21, 22, 24, 24, 25psi?
Here is the link to the thread on where to buy the lifters.
http://www.skylinesaustralia.com/forums/topic/361912-hydraulic-lifters-noisy/page__view__findpost__p__5776895
http://www.rockauto.com/catalog/x,carcode,1209844,parttype,5548