2008 Grand Prix, Base 135,000 miles, auto trans. I replaced spark plugs about 6 months ago. Engine ran just fine. No codes. I recently decided to clean electronic Throttle Body as I noticed it was quite dirty/gummy black stuff. Removed Throttle body and cleaned with throttle body cleaner. At that time I noticed additional dirty/gummy black stuff in the plenum, which I also cleaned inside as much as possible. Also removed EGR and sprayed with TB Cleaner as well. While I was at it, I used Mass Air Flow Sensor Cleaner for the MAF. Now the engine runs a little bit rough and engine light blinks when I accelerate. Additionally, car now throws Code P0305. Is it possible that I might have clogged a fuel injector during the cleaning of the Plenum? If so, is there a DIY method to clean the injectors? Any ideas are appreciated. Thank you