Different things besides the ignition can cause a cylinder misfire. How many miles are on the car now? The V6's don't require a plug change until 100K miles. You can start with doing some diagnostics to eliminate things without spending any money. First, clear the code from the PCM. Swap the plug from cyl 1 to another cyl and see if the misfire code moves to the other cyl. If not, swap the cyl 1 coil to another cyl and see what happens. If the code stays with cyl 1, something else is creating the misfire. If the code moves with the swapped component, that is the problem part.
Heavy carbon buildup on the piston, a clogged injector, a marginally working O2 sensor, a vacuum leak - any of these can cause a misfire.
2006 Inferno Red SRT8 with groups I, II, Sunroof, K&N drop-in filter, Auto-dim mirror, Jet-180 T-stat, Predator, 300 SRT struts/springs, Chally SRT wheels.
Born 6-21-06, Home 4-26-10. 1/4 mile - 12.989 @ 108.78 in street trim. Traded 10-19-2012.
2006 Inferno Red R/T with R&T Born 8-12-05, Home 8-25-05, Sold 8-9-10.