Check the spartk plug wire resistance too. Should be no more than ~10000 ohms per foot. For example, a good relatively new wire ~ 3 ft. long will have a resistance in the neighborhood of 12000-18000 ohms. If any of the wires are marginal/bad, replace them all. You may also want to consider the Tayor Shorty wires, which eliminate the long wires and the failed "Wasted Spark" System. Since you're getting misfire codes, I doubt the problem is your EGR Valve but, if it has lots of miles on it, you may want to consider changing it just for giggles. Some of us have now put this on our "time change" list for around every 50-60K. Part is only ~$30-50, and after the first time only takes 15-30 minutes to change. A bad one will affect idle quality, performance, fuel economy and, as R32R1 said, you'll get surging from ~35 >. If it's bad, you won't always get a light either, until it has gone completely berzerk.
06 GCO, Dk Khaki, QDII, Flshing Hi 3rd Bk Lt, MDS "ON" Lt, Airtab Vortex Gens, Debadged, Fumoto Drain Valve, BT Catch Can, Chopped EGR Tube, SRT8 CAI, K&N Filter, Sonnax Trans Line Press Booster, SC Tuner W/Adv Trans Tune App, DS Tuner, Cust tubular hdrs w/3 in Magnaflow/Xlerator AP Exh Sys, Bilsteins, SRT Springs/Sways, Cust Eng Cvr, SRT8 frt/rear bumpers, FRI Sidewinder Cam/6.1 valvetrain, SLP 25% UD Pulley, BBK true 90mm T-Body, SOS Ign Coils w/.060 spark plug gaps, SRT Reps with 265/45&295/40X20's.