having done one now i wouldn't hesitate in doing another.
Me, doing it on my own i would budget for 5 days;
Day one: back end, paint and install filler and filler pipework.
Day two: Injector nozzels, injectors, wiring ECU
Day three: Vapouriser and water pipes
Day four: Front to back pipes (without a ramp this can be a real pain in the a$$) interior guage and switch and finish off any jobs that havent been done or that have cropped up.
Day five: test run, set up
I have most likely overestimated here, in reality if you were really getting stuck into it 3 days would be possible, so long as everything was to go in your favour.
If you were doing it yourself i would recommend these chaps:
http://cgi.ebay.co.uk/MOTOGAS-AC-6-CYLINDER-LPG-INJECTION-GAS-CONVERSION-KIT_W0QQitemZ330206222019QQihZ014QQcategoryZ36631QQssPageNameZWDVWQQrdZ1QQcmdZViewItemJames and i have used them, that kit he has there is just the front end kit, you will need to add a tank to that as well, i paid £705 for the whole lot, and that was with a 70 litre tank, although i wish i had gone for a larger one now, mine has done 6/7000 miles and everything is still good
I have seen a couple of people with 100l tanks, but have they got them in an Elite, don't forget you will lose a bit of space due to the bose amp in the back shelf.
If you need help there are enough people on here who have either done one or been involoved in a conversion
