Hey, I also have a '93 jeep with 4.0 I6. I've been having a problem with gas milage, i used to get around 18MPG and I'm now getting 15MPG. I've replaced the valve cover gasket because that was leaking and the power steering pump (which will need to be replaced again since it is squealing). I would like to get it back up to 18MPG or even better. I noticed that the engine ran smoother durring idle but after 30 minutes of driving the valves are tapping loudly and I loose some of my horsepower. I'm thinking timing... ???