I have a 2001 Cherokee. It has been lifted 4" with 33's on it. Still in progress of doing many more mods. I keep getting the P0304 code which is cylinder 4 misfire. I have changed all the spark plugs with top line parts. I also changed the long coil pack as it is the 4.0L straight 6. I still keep getting that code coming up but it doesn't seem to be running poorly as you would think it should with a cylinder misfiring. Although my gas mileage is horrible it is around 10 miles to the gallon. not really sure what else to check. could use some advise please

 

How did the number 4 plug look when you replaced it ? I assume you got the code before and after replacement ? If it seems to “run fine” besides poor mileage and check engine code I would check compression .