mgmz28

My car is a 98 z28 m6 with about 75k on it. The only mod I have done to it is make it into a true dual, stock headers with magnaflow high flow cats, x pipe and 2 borla xr-1 mufflers. The car was running real good till about a week ago when the car started misfireing real bad. The service egine light came on but it was flasing on and off when i gave the car gas, something i had never seen before. I drove to the nearest autozone and ran the obd ll on it. It came up as code P0305 cylinder 5 misfire. I bought 8 ac delco irriduim spark plugs and I'am about to change them out. Do you guys think this will be the problem, or is it something else? Some feed back would really be helpfull. Thank you.

2001NBMZ28

Least you know what cyl it is, I'd try changing just that plug/wire first and see if the SES comes on again for the same code.