Sequential gas injection for 99 VT SS Commodore

I'm not aware of any reviews of such installations you could refer to. Vapour-injection systems weren't around when the VT was launched, so it's unlikely many have been fitted with them. I've driven a couple of later model Commodores with the Gen 3 V8, like the engine in the VT II, that have been fitted with injection systems and they have driven and performed well. If you want to find out more about them it's best to talk to the system manufacturers directly who should be able to put you in touch with owners who have had the conversion done.