My 94 2WD 4Runner has the weakest V6 engine I have ever had in any SUV I have ever owned. Gets terrible gas mileage, about 17 HWY, 13 or 14 around town. It has a factory replacement engine with 45000 miles. The engine was a free replacement because of the recall on these engines from 90 to 97 models. It started with a head gasket recall but that was not working so Toyota went to full long block replacement. I got lucky. Mine blew up in the middle of nowhere with 215k on the original engine. They came and got it, put a new engine in it and charged me 600 bucks for incidentals. That was 4 years ago. I don't think any of the "BIG THREE" would stand behind a vehicle like that. That being said, what can be done to get a little more power out of this thing??
What size tires do you have now?
If 17 HWY, 13 or 14 city, is with an auto trans and 3.90 gears/stock tires, that is pretty good, a manual would/should only be about 3mpg's better.
Swapping to the 4.10 3rd should help with the city mpg's, as well as hwy if it is an auto, if manual it may not help with the hwy miles depending on your cruising speed and tire size.
With the detuning of the heads by Toyota, power/mpg gains isn't cheap to do with the 3.0, no one mod will yield much, so figure on spending around $1000-1500 before you find any real gains.
