how much are new lifters? are there better aftermarket ones that support higher revs?
I just put some in with like 60k miles on them, cost me $250 for em. they also included a cracked head, cams, and a good e36 m42 head (smaller valve stems = higher reving?)

OEM lifters are about 22$ each x 16 is about 352 + tax (these are canadian prices). the aftermarket ones are softer, and are prone to failing (i spoke with several mechanics, and i know the guy who owns the shop that ground my cams).
if anyone needs any i have a fair amount of low km ones sitting in my room.
edit: also, they can be reconditioned for about 15$ a piece. the heads on them wear out, there should be a very small dome on the top, you can check them with a straight edge and if there is a small dome they are ok, any dome is fine. if they're flat they need to be machined (a cam shop should be able to take care of that).
i'v been hearing talk about upgrading the lifters with other bmw ones, but im forget the details... somone else should be able to help out with that...