personally the spool up is much better than most turbos. Lighter flywheel, the split dp and of course the fact the PE1420 are BB all play a role. IMO, the spooling takes a fraction of a second longer than stock. Negligable really. Just the look on the guys face after you blow past hime makes it all worth it. I haven't dynoed my Z yet but I will after all my other mods have arrived and will post some additional long awaited numbers. Kudos to PE1420's...thanks Chip!!!