I have a 94 js 2x4 4dr 16v that I converted to a 4x4, I had the exact same problem that you guys are having. Clean the inside of your throtal body and the vacume lines that lead to it, and try some "Heat" in your tank every once in a wile when you fill up. Mine is running like a sewing machine at 160,000 miles. There is one vacume line in peticular that connects to the top of the body, the opening is about the size of a pin. It gets plugged very easy, after cleaning your computer will need to relearn how to run your engine. I hope this works for you.
Good luck