I plotted some boost levels against a rough calculation of a VHR for the gt2860 (stage1/2 turbos), gtx2863r and the gtx2867r.
if you plan on never making more than ~575whp (or dont mind running meth/e85), the gt2860 is a great turbo for 15psi or less on our engine. after 15psi you start entering the choke area of the compressor at high rpm (6k+) which will shorten the life of the turbo and blow hot air. (i don't have this graph handy but trust me, its choking)
If you're going for more than 600whp, the gtx2863R is a much better match, at 24psi its in the choke area up top so I wouldn't recommend running a lot of boost with this turbo on 93. still a great turbo for our engine and should produce 650+whp
in my opinion as far as efficiency is concerned, the 2867r looks like the best match for our engine if you want make power past 600 but still have a quick spooling turbo. these wont start running into the choke area on our engine until 25psi near redline, at that point you'd be producing somewhere near 700-750whp.
