I have a 1990 xj with the 4.0 engine.It seems like it is running rich.It doesn't smell like gas it just kinda makes your eyes water after a little bit.I have already replaced the 02 sensor,and the tps.I have cleaned the throttle plate and the IAC. It does run better than when I first bought it.Possible problems are,there is a slight exhaust leak at the header pipe by one of the collectors,and the o2 sensor is located not where I think it should be.It is way downstream from the header pipe.It is about 8" to the right of the drain plug.Also the cat seems to be original.It runs good "a little rough at idle" but otherwise pretty darn good for having 187000 miles on it. Any ideas would be helpful.