I have recently found out that the sequental vapour system is better suited to cars with a digital computer and been told that the 96 el fairlane I drive has an analouge comp. so I should go with the single input system and at $1000 cheaper it sounds good to me aswell. The sequental Vapour system would set me back $4000.

The maximum power loss is 5% in some vehicles however most modern vehicles put it on a dyno and I think you will be amazed. Most people perceive less power because the gas is vacuum to the cylinder after supply where petrol is injected just above the valve and is more volotile making it feel more punchy but the dyno figures will blow you away.
I had a 351 I put on gas and the cost got back to me in 9mnts it depends how many km you do and how thirsty the original engine is. I changed the cam to a gas specific cam and regraphed the total advance. i was running 20 degrees at idle and total advanced to 32 degrees. After these two changes it ran harder on gas and would ping on petrol after over half throttle. The vehicle weighed 2000kg with 2.75 diff,FMX and would accelerate from 140km/h to over 240km/h over 900m, try that one at home with all that weight. My fuel bill from home to toowomba went from $130 to $70 about 1000km so every thou I would save $60 which equates to 35000 to 45000 km to pay for itself on installs of $2200 to $2800.

well driving in bumper-bumper traffic 14.9/100km & 13.0/100km no traffic