G'day Tony and the rest of yooze.
Our van is dual fuel on the good old solid 202. We had the 253 in the Panno when we got it, but threw the 6 in for economy and for the fact that our 202 was brand new. We didn't know what the history of the 253 was.
The 8 was tuned up for gas when we got it and when we ran it against the petrol 8 in my ute, there wasn't much between them in performance.
With the 202 gas and petrol differences are minimal out on the open road. The thing is now tuned up toward the gas, but not so much that it looses out on fuel. We have a long legged diff and LPG suits us for long distance driving. We switch to fuel when we hit the edge of town to give us a bit extra poke on the lights and we find fuel is more drivable for stop-start driving.
We had the system checked over well when we bought the van, and our mechanic tidied up the hoses etc. now the carby runs a standard looking air filter and the hoses are tucked away for a clean engine bay.
I usually have a yarn when I see anyone filling their old Holden at the LPG bowser to see how they run and hear a full spectrum of pros and cons. My dual system starts better in cold weather on gas than petrol. It doesn't like hot hot weather slow driving and often splutters if you are around town on a hot day. Power is better on fuel (I run premium) but a get damn good economy on gas and it seems like I can drive forever on a full 65 litre tank. Combined with a half tank of tiger, we can head most places without gas and know we can get to the next place that has. We have no problems switching over between the two on the go.
I would like to hide the spare tyre out of the back, but the problem is minor compared to the savings on gas.
Shop around. The job that was done on our van was a sin and whoever did it should throw their chainsaw in the bin. It was a shocker.
There's me two bob.