Rough idle ,,,various other problems

i have a 96' explorer , the previous forums have helped me out considerably ,my concern is that my x likes to randomly chose when to idle roughly ,,,even at a good operating temp., so im still confused on wether it is simply dirty injectors ,,fuel filter (not so serious) or those plastic "o" rings on the intake ,,,causing a vaccume leak. There seems to be many solutions to this idle problem ,,,i would just like to narrow them down.

Check the PCV. Clean the IAC valve or replace $45.00 at Napa Auto Parts. I do this first since it's not to expensive. Injectors are expensive. Also check out that vac. hoses are not disconnected at the intake manifold port connectors or that there are missing vac. caps at the port. On the 92 - 94 4.0 it's a common prob.. Power brake booster, trans vac. modulator, and a few other lines connecto to the port. Located driver side of intake near firewall (91-94). Let us how it went.