If you press hard down on gas pedal check engine light flashes no power

Hello, flashing check engine lights typically indicate an engine misfire. Due to the high miles of the engine - it's really unclear as to what the root cause is until testing is performed. Yes, spark plugs and coils and fuel injectors are possible causes, but so is the valve train and base engine itself. Has valve adjustments been performed on a timely schedule? The dealership or any repair facility will have to test to find out what is going on. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops

What location is the coil you replaced? Is it on the front bank (closer to the radiator), or the rear bank (by the firewall), IF it’s a 6 cylinder. Did you change the spark plugs when you changed the coil? That $160.00 the dealer wants, to (theoretically) diagnose the fault(s) correctly, may save you hundreds more in incorrect guesses. IF you choose to respond to either DaveJM or me, I’m sure we can try to walk you through further basic diagnosis, depending on what tools/test equipment you are working with.