engine noise

I recently purchased a 98 xlt 4.0 sohc with 62k. it drives nice, however the idle is sometimes a little rough. check engine light came on under moderate acceleration 3500-4000rpm. (misfire cyl 3 and 5) plugs and wires have been recently replaced, i cleaned the maf, and replaced a very dirty air filter. #3 plg wire looked a little short going into the coil pack, and had green corrosion. i guess i'll try a new set of wires and ditch those bosch plugs for a set of motocraft. my real issue is this: with a warm engine i hear an intermittent strong ticking at the front of the engine especially upon restart. it sounds like a lifter but the idle's usually ok at that time. there's a recall and extended warranty on the cam guide. does anyone know what that sounds like? i don't expect a lot of free help from ford unless i go in with a positive informed attitude.
thanks you folks are great

Timing chain noise on the 4.0L SOHC engines sounds like a cross between a clatter and a spark knock/ping. It's usually evident between 2500-3000 RPM. Sometimes they make noise at idle, but I wouldn't describe it as a lifter tick at low speeds either.

possible valve tapping?