Nope, sorry I'm still none the wiser. I think it is the 'GNU' that has made matters worse.
I understand 'gubbbins' though 
Can someone explain this upgrade in really 'thicko' simple terms and what it does to performance?
Why would someone want this to be done?
Sorry ... GNU -- is what I call my miggy (reg letters). She has an old, outdated and badly performing LPG mixer system with one injector. On V6's ( which my car is) this system is prone to bad running and backfiring on LPG. A backfire can split the intake pipes ( which happened to me a couple of weeks ago )-- or blow the air box or Mass Airflow Meter ( methinks).
The sequential system doesn't backfire, runs smoothly with no noticable drop in power or MPG, having an injector for each cylinder, and is generally more reliable and far easier to set up and keep in tune.
This is how I see it -- could be right up the wrong tree as all I know about LPG systems is written in this post !!!!