2000 Honda CR-V Question: Misfire codes and rough idling at stops

I have a 2000 Honda Crv with about 201000 miles on it. Runs great at higher speeds, at low speeds in town and at stops runs rough and shakes. Codes on scanner are the P1399 and the engine 1 misfire codes. We have tried the tune up items such as plugs, wires, distributor cap, air filter, fuel injector cleaner. Runs a little better but still the rough idle. Not sure what to do next. We did not use the NGK plugs because I wasn't aware that I was supposed to buy those, would that make a difference or should I go straight to having a valve adjustment done. Running out of ideas and would like to not spend everything I have on repairs. Check engine light stays on while driving at high speeds and now flashes at low speeds and while stopped.