97 LHS Rough speratic idle

Check engine light keeps coming on and it comes back as a cylinder 5 miss fire which causes the car to idle like crap. Brought the car to my mechanic on a few occasions, the first of which he replaced a bad fuel injector but the problem still persists. Second time around he replaced the EGR valve which was on its way out. third time around and we're both stumped. Plugs and wires are fairly new. Anyone have any suggestions? Anything would help at this point.

thanks guys

Have you checked compression and spark intensity?