I just bought a 2003 Mazda Protege DX Manual transmission 135k miles and have been having issues with rough idle. At emissions it threw a p0303 CEL light for cylinder 3 misfire.

I noticed a small pool of oil near the #3 spark plug boot, took boot out, fair amount of oil on it as well as oil on #1 cylinder boot. #3 spark plug looked the worst of all 4. Replaced valve cover gasket along with dabs of RTV by sharp corners near cams, spark plugs (NGK V-power), and I removed EGR valve for a good clean (soaked an hour in carb cleaner, oiled valve shaft, replaced). Also cleaned out PCV valve as well. Computer has been reset several times, always disconnect the neg battery cable before working on cars,

The car still gives me rough idle after being warmed up, it actually almost stalled for the first time today after EGR clean.

I have searched on this forum for rough idle threads, EGR clean, etc etc. I was just wondering if there is anything else I should try before I buy new coil packs and wires?

TIA,
Thomas