I have a one of those newskool slip in diffs (PG copy) had it installed for like 10k miles so far and its seen 2 drift events with all that crazy tire spinning its held in there. I recommend it, you can definately tell the difference handling is better launches better drifting better.

I installed a PG in my 280Zs diff and I notice it slips a bit even with the XTREME springs. it wasn't as smooth as the 2gnt install either I had to sand the gears down so it'd fit. I haven't really done any real drifting in the car yet though. So PG unit seems a little less nice unless you get the mega strong springs.

what exactly is a retro fit? I know there's that OBX one but I heard that's crap.