I found this earlier this week on ebay:
It appears to be rare because no one else is selling it right now and they're usually included in shop manual sets on ebay... this little book wasn't cheap but it was worth it!
It completely covers in details the significant differences between the 2TZ-FE and 2TZ-FZE, as well as other interesting little details that makes the S/C model much different. The improvements were for reliability in mind.
Anyone interested in scans of some of these pages? It'll take way too long to type out. I don't think it's reasonable to expect everyone to buy this when it's both rare and not necessary for reparation work of their Previa.
Also.... if anyone is looking for a 94 Previa shop manual, make sure it includes the supplement shop manual (same orange striped black cover look as the main manual)... this supplement shop manual covers the S/C model stuff, the main shop manual only covers the non-S/C... if you want a single manual solution, then you'll need a 95 and up manual it appears