4x4's are never great on MPG's but the carb is the biggest cause of that. As I mentioned in another post, the Weber carb does everything better than the factory Mikuni carb. Yes it can be fiddly to get the engine tune right but once it's there, it's more than worth the effort. Getting rid of the water pump driven clutch fan and installing an electric fan will help as well. It'll cool the engine when it needs it most, takes a load off the water pump and de-governs the engine enough to improve throttle response (added bonus of freeing up some engine bay room as well)