After much deliberation and research, I've taken the plunge and had my car converted to LPG.
Historically I've had several cars over the years on LPG, all on the Prins system, and overall it was a good money saving exercise.
One car wasn't so good initially, mainly down to me choosing the wrong installer who didn't do the job properly, which left a bad taste in my mouth and put me off somewhat.
However I did more research, found a great local installer who resolved all the issues and restored my faith in the whole idea.
Now the 3.2 Audi engine is a direct injection, and there is only one supplier out there that does a kit specifically for this engine. The difference is that with DI the injectors are not in the inlet manifold and to cut a long story short the system has to run on both petrol and gas to prevent damage to the injectors. So mine runs on 95% gas and 5% petrol.
After much deliberation I decided to go ahead (knowing after a years ownership the car was in good shape) and chose a local installer that I know to be excellent in his skills, attitude, reputation and approach. He always has some seriously expensive cars in his workshop !!
Initially they had done one before when the kit first came out and had some teething issues with fault codes being thrown up which Prins got involved with.
I know other people with the same car that have had this conversion and they are well pleased with it, so I ensured my ECU software was the same level as theirs, and already knew the basics with my car were in good shape, including new coil packs (foc recall), new plugs, new thermostat and coolant.
The install requires considerable man hours to install so took several days. This seemed a long wait but worth it.
From the word go the car has driven without fault, smooth as silk, and cutover is very fast. You cannot tell it's running on LPG unless you look at the LPG gauge.
Out of the 3 cars I've had on LPG, this is by far the best conversion both in install quality and running. It even fills quickly with no drama. Just goes to show how good LPG can be if all is done properly.
The installation itself is very neat, all connections, plumbing etc are done properly and well hidden.
The tank replaces the spare wheel and is 76 litre capacity, so 80% is around 60 litres.
Had this for 4k miles so far and figures looking good. Originally I was paying an average of 26p a mile on petrol.
So far I'm averaging 12p a mile on LPG, often as low as 10p (depends on journey type and cost of fuel of course as both these vary) and 3p a mile in petrol.
In summary I was nervous about the whole thing, but am very pleased it's now done, it makes a large petrol engined car affordable and no drama's so far. Hope it continues.
There are not many posts on the DI engine so hope this helps others looking to reduce their fuel costs.
More info and pics here:http://www.vwaudiforum.co.uk/forum/showthread.php?145058-3-2-FSI-Prins-LPG-Conversion
Subsequently found the Prins ECU isn't in the plenium chamber after all ... Good idea on these cars as like many others they can flood if the drains area not checked and get blocked.
I did speak a while ago to Tubbs about it but it seems only Prins do a system currently. Repaid with the plug for Tubbs on the other forum - one day I'm sure we will meet !