Hey all, first off I have a 98 XJ 4.0/5 speed 4x4 with 254k miles and still love it. However, in my 4 years and 40k miles of owning it, it has always displayed an intermittent P0301 code and CEL (cyl 1 misfire), but always ran great with a slight miss at idle as well as a rough idle. About 2 months ago, after a worsening rough idle, the CPS went out, and I replaced it with a NAPA Echlin part. Ran great with no CEL and no rough idle or miss at idle for about a month, then one day the P0301 code came back and so did the rough idle and miss. The CEL is now constantly on with P0301 code, and the rough idle/miss is the same as before, if not slightly worse. I have checked compression, switched injectors, has new cap, rotor, wires, plugs, popped the valve cover off and verified valve operation, seafomed, listened and sprayed for vacuum leaks at intake manifold, etc. It has all checked out. Rocker arms are still shiny and all cylinders have good compression both cold and warm. Ran it with the serpentine belt removed for a minute, engine runs quiet as new. I can still roast the tires from takeoff, but it won't pass CA smog like this and is therefore a major problem. I'm at wits end. Any suggestions? Timing chain maybe?