1999 Honda Accord Ongoing Problem

I have had a similar problem occur over and over again. A couple years have gone by and I have replaced a wide assortment of sensors and my timing belt, tune up including replacing rotor cap, wires, and spark plugs, and the ignition switch(which was recalled on this model.) The cars idle drops when in park, but not stalling out. when I am driving up any incline the car sounds like it doesnt want to go, a hesitation and the check engine light flashes continuously. When hooked up to a computer, it says its an ignition missfire but as said before spark plugs and tune up has been done. Any ideas?? The problem is getting worse!