Review on ACDelco 17 Professional RAPIDFIRE Spark: Ultimate Performance for Optimal Ignition by Mario Beats

Bought new AC Delco coils and these spark plugs. Everything seemed to be going smoothly, but after starting my car I immediately got a flashing check engine light indicating a misfire. Removed all coils and reinstalled, assuming I didn't install the coils correctly - no improvement. I then removed all the new coils and reinstalled the old ones as they worked fine. I did it as preventive maintenance for 184,000 miles, no improvement. Did a little research online and found serious problems with these forks. DO NOT BUY THESE. DO NOT ACCEPT THEM IF THEY ARE FREE.