Engine Miss

Engine misses under load. Cruise along fine and when going up a long hill and just before it downshifts.. I get a missfire and some times a short backfire. once it downshifts,,,,no problem. I noticed this on a recent trip to vermont. Have 101,000 miles. other than that it runs just great.
I run regular gas, as I have for years. I averaged 26.6 MPG on the trip.
Any ideas where I could start looking.

when was your last set of plugs and wires?

I had the same problem. Replaced plugs and wires (OEM) and the problem was better, but still there when the converter locks up under gentle acceleration there was a miss. No codes or SES, just a slight miss. Bought a new coil and changed out one at a time with the new one. The third one was the culprit. That was two years ago and the same thing has started. I am going to order another coil and try again.
I run regular gas most of the time also and get around 25/26mpg highway.

i`ve always found one of the coilpacks bad causing this.

One day I hosed down the motor with engine cleaner and mine missed for 30 minutes, nearly going dead several times and check engine light going crazy. Not sure why a small amount of water would cause the engine to go bizerk but after a few miles it cleared up. I guess these engines are not waterproof and I'll never clean the motor again.

Cover the coil packs and connectors with a plastic bag and you won't have a problem.