I'd say it the head design influencing the compression...as with the RB20DE Neo it's called a lean burn head, just an assumption there
Specs for most of the parts would be available in the Nissan parts CD...which has been mentioned for sale but no-one followed through on it.
There has been some info floating around, the NEOs are meant to have solid lifters...unlike the previous counterparts and actually have oil squirters in ALL models. I've been running the turbo on my engine now for 20,000k's with no related problems (the coil packs were just shite!) My engine has now done a total of 130,000ks and I'm confident of it making 200,000...we'll see cause I'm keeping her until she rusts away...or the trade-in price on a 350Z isn't too bad
I'm very keen to get to a dyno if anyone knows of any dyno days in the near future