Sorry, not sure about the details on the LPG system on my EB fairmont, but i notice a slight decrease in power on LPG, particularly in the lower rev range (doesnt idle as smooth on gas too).
When driving around its not too noticable, but when you put the foot into from a stand-still, there is clearly more power on petrol.

After reading the question and answers, I notice a few errors and assumptions that should be cleared up here!
Firstly, it must be remembered that petrol cars were designed to run on just that...petrol. ULP has a lower compression ratio then engines built for super but ULP engines have superior ignition systems which don't require upgrading. In fact, for LPG, ULP ignition systems are great! EF, like AU's use a coil pack with many of you would know, but understand that the output of a coil pack is as high output as you'll ever require.
Saying that, LPG require only one thing that Falcon engine were not produced with, High compression ratio..!!
LPG really starts working at an optimum level from 11:1 Comp ratio onward if you have the hardware to handle it and survive everyday driving and expect your engine to last!
If you’re running a duel fuel Falcon, the figure shouldn't go much above 9.5:1 compression because ULP doesn't like it and will experience detonation which will really ruin your day! This is the dilemma of duel fuel ULP engines with has been a bit of an issue since 1985, a year before Falcons were ULP only. Pre ULP engines on the other hand don't have the same problem to that extent because they were designed at around 9.5:1. But Super is dead (the real lead super) and about the only real worthy option is PULP (premium). If you use PULP and boost the compression ratio to 9.5:1 or even slightly more (your call) you will have the best of both worlds for a duel fueler and get the added power you’re after!!
An LPG car that has a noticeable difference in power from a standard engine is a dodgy LGP system that doesn't suit your application properly!
A Falcon isn’t tunable!! Only by fitting an after market management system can you tune one. It's the LPG that needs looking at in that event, not usually the car if all else is good with it! Straight gas rocks!! I have built a few and one was 380 RWKW and was a stoking hot son of a B.....!! I loved every minute of it!!
My advice is buying a dedicated LPG AU and pump it out to 11.5"1 and through in as big a cam and exhaust as will fit as these baby's don't have anywhere near the limitations that a petrol car has! Have fun.....x-dub

I'll tell you what I get after the cam install.

Last dyno run I got 99.4rwkw ... and that was with 2.5" cat back exhaust only.

Snce then have had extractors fitted ... will be getting the intake modified .... and as mentioned ... getting cam installed ... will be interesting to see how it goes.

Also had a new strengthened auto installed ... this might actually help too .... in a way.

Errr.... have you heard of the Ford Flash Tuner?

AU I wagon - CAI, K&N panel, Paceys, 2.5" system, Crow 2232549 and Chiptorque chip, Sprintgas system, 175rwhp which is about 129rwkw.

Flash tuner for the pre BA engines is only a recent development.

It's been around (and heavily advertised) for AU's for at least 6 months. Bear in mind that the oldest of AU's is now 8 years old. The dribble I quoted before was posted 2 days ago.

IIRC the CAPA Flash tuner does not work on EGAS ECUs ... as they are setup differently from the petrol version.

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Hehe sum1 else from lara sleepy old town isnt it

as he said,but in usa the compression ratio is 10.3-10.6 to 1,but you have to use a gas cam,as the overlaps and design are different,check out crow cams--for gas and compare to petrol cams,gas uses half the advance and different spark curves,and you have to use 98ron on petrol----then you can make 30-45% power increases,have fun.

there si a HUGE difference between gas and petrol on my car, when i flick it to petrol and accelerate tis like im in a compellety different car, and thats not exaggerating. although i have to say even on fuel my car runs like a dog. its werid u floor it, it kicks down as it hits 3k the rpm needle starts dropping back instead of going hard.... BUT it saves me alot of $$ on fuel and i dont hammer it much at all so it doesnt bother me.

what is the car tuned for gas or pulp.i think you have a pulp tune and trying to run gas.pick one and tune it, i tune gas and pulp is slugish,gas is #1 used.

The first BA LPgas only engines have 10.3:1 comp ratio, and heavier conrods & better pistons, the series 2 BA raised to 10.7:1. Ford had 25 EL falcons driving around in Melbourne trialing CNG (compressed natural gas). They were running 13.5:1. they were proto-types. Haven't heard of what happened to them. That was a few years ago now. A friend of mine was working in Sydney back when XE's were new, and he new a guy from Ford who was a test driver, and he brought in an XE sedan for an oil change, when my friend hoisted the car, he saw the auto trans wasn't like any he'd seen before, years later, when the 4speed auto came out in the EA's then he realised what it was all those years ago, 1983.
There are heaps of prototypes running around and nobody nows, except the guys doing the projects.

1992 EB II GLi Falcon with just a 2.5 Cat Back Exhaust on LPG registers 118kW, on a 2 week old reconditioned 4.0L motor. That also has a BMC hi-flow panel filter too.