Auto gearbox problem

Well, I'm pretty good about changing my oils, so, given that the vehicle is new to me, I think that changing the ATF can go on my list along with the timing belt, fan belt, diff/swivel/transfer box oils, engine oil/filter, bleed brakes, brake pads, change coolant, whip props off and grease 'em and anything else that springs to mind

OK, I've tested this whilst locked in to 3rd gear, and I'm still getting it seem like it's hunting for gear, although I still suspect an engine fueling problem more than an autobox problem. The investigation continues!