you are jumping all over the place to conclusions that are unsubstantiated. First of all you need to let us know what the code was to do the proper procedure associated. Always start basic, and jumping to change plugs because it "felt" like a misfire was jumping the gun.

Because you sneeze or have a runny nose doesn't necessarily mean you have the flu... need to do all the checks to find out it's not a cold or allergies etc