I've got a 4 month old
diesel SR5 manual and I LOVE IT!!!
I regularly get 7.7L/100km when driving to and from work, mainly back roads at 70km/h, few traffic lights but plenty of hills.
Drove to Bathurst last year not long after getting it and it did 10L/100km with a trailer on the back (sitting on 100/110 most of the way), which was better than my mates
Diesel Auto D40 Navara which did 11L/100km without a trailer!
Weigh up the costs of
petrol servicing, fuel costs, etc.
A few people have had problems with valve seat recession though after converting to gas...
Personally I'd stay away from converting to gas.
I hope this helps.
Cheers