I don't know how much better you expect the milage to get with the SC but its only gonna get worse. With my 3.0 rebuild I find I'm getting a little better milage but I doubt I'll ever get close to the 3.4. Maybe tuning with MS will help things out somewhat. The truth is that the 2.4 and 3.0 aren't what you could call very efficient designs.

If you want my opinion the yota diesel swap is the way to go for sure. I wish I had done it. The cost would have been less or the same as a 3.4 swap, useable power would be about the same and milage would be better. There was a thread here about swapping a VW diesel somewhere that I thought was really cool. Perfect for a 22re equiped truck.