In my last Ranger, an '03 4WD S/C with 4.0L and 5 spd auto 4.10 gears and 32" tires, I had installed a jet chip to compliment the AEM CAI and JBA exhaust. I was very pleased with it. While they suggested using at least 91 octane with it, I never noticed a need to, no ping and it ran strong. At first, with these mods, the only thing I felt made a big difference was the CAI, but after driving a while under different conditions, I could see where everything improved performance. I also didn't install them all at the same time, but over a matter of about 2-3 weeks.
No mileage gains that I could ever see, but I never drove it in a manner that would have shown any sort of mileage. Shifting definitely changed, and on a kick-down you could really feel the improvement. I also noticed it when pulling a steep hill from a stop; it wouldn't strain at all, it just kept accelerating and upshifting. I also noticed the improvements when coming to a stop light. If the light turned green before stopping, my Ranger would launch very strongly, sometimes even breaking the rears loose and keeping them spinning into second gear.
I currently have an '05 F150 2WD with a 4.6L and 3.55 gears, but I miss my Ranger. I've done similar mods to my current truck, including professional programming, and the ranger with those mods would still have run circles around this truck. My current truck can't even break 'em loose unless the pavement is wet.
I'd suggest if your curious in a chip or programmer look at Autoanything.com for a price, they're usually among the cheapest if not the cheapest. They also will refund the difference if you can find it cheaper anywhere else. I used them for most of the stuff I have bought for my trucks and know they honor their price guarantee, as they did for me quickly when Summit put the same item on sale a week after I bought it from them.
Keep in mind, most programmers are designed for a stock vehicle, not one with modifications, especially CAI's. This also will affect your air/fuel mixture ratio, possibly causing it to being leaner than what is ideal for you engine. You should scour the websites of those manufactures to be sure that the programmer/chip they offer accounts for some common modifications to avoid these undesirable conditions.