my car has been sputtering when you give it gas, i have been getting a misfire cyl. 1 code

i have narrowed it down to a few things i think it could be and why i think they are the problem.but figured i would see what others thought it might be

#1. ICM, mis-fire on cyl. 1 even though it could be 4 also but its hard to be sure with dis. there have been maybe 3 times in 2 weeks that i havehad a mis-fire on 5 pop up on the scanner

#2 egr valve, egr isnt used when the engine is cold and it runs fine until its warmed up and i know it hasnt been cleaned in over 4 years because the person i got it from never cleaned it. also could i just get gasket paper for this since i have to special order the egr valve gasket

#3 cat. converter, because it doenst start acting up until the engine and everything warms up and its the factory cat with 110,xxx miles, so once the exhaust system is nice and warmed up everything in the cat would start expanding(in my theroy) and then start cutting powerBUT the reason i think this wouldnt be it, if the cat is clogged wouldnt it not run at all when it was at full operating temp? unless its only half clogged and im hoping this isnt it because its the most expensive of the 3


now the part that i am lost on, egr isnt used at wot and the car quits bogging down once im past 3500-4000 rpm but it still "pops" and backfires even once im past 4000rpm

everything on the ignition except the icm is new and my mechanic checked everything and agreed with the three things i narrowed it down to, i would just have him figure out what it is but he left for 2 weeks on vacation and i need it running better ASAP

also its a 98 3.8 and i have no idea how to clean the egr valve on these cars so any info on that would be appreciated