I have a King vapour injected system fitted. They're built for sequential however E series are batch fire so you don't get the full benefit.
Lucky I had an honest installer because there were major issues I had to have sorted which were done at no extra cost. Misfiring and flipping into Limp mode. Val-Tech injectors replaced. Wiring redone. Would have cost heaps. Not sure what brand injectors now. No visible brand name.

Initial fuel mileage was excellent. 420km per tank (65L) around town. 580km on long highway trips.

System cost was $3900 fitted. Did it back when there was a healthy gov rebate.
Has paid for itself now some year and a bit later. Finally reaping some savings while everyone else gets fisted with petrol prices although the new head and other car expenses have been painful.

Head gasket blew shortly after a cam change. Replaced head with a Tickford and put AU injectors in and now its all out of whack. Mileaged dropped to 370km so I'm in for a ecu chip and Dyno tune.

Don't bother getting LPG if you want power. Esp 200rwk. My system automatically switches to petrol over 1750 rpm then back again quicker than you can blink when you take your foot off the pedal. You don't even notice the change under heavy throttle. You can adjust the threshold point but 1750rpm sits nicely with cruising gear shifts.

If your system can't support LPG above that it is insanely undersized for the engine.

You sure you don't mean 3750rpm? Otherwise as tickford_6 said, it's way too small & you should be complaining big time about the system.

Cheers

ToranaGuy