1990 Nissan Pathfinder totally stock "survivor". Well maintained with 200,000 plus miles but run well. About the only upgrades that I have found on it so far is a rear receiver hitch. I am going to put one up front as well for various reasons.
Have you pulled the spark plugs yet? So often in these cases it ends up being a burnt or partially disconnected plug wire or a dirty or misfiring plug. I just sold a Ranger with this very same problem.