Good start, but just because you added some injector cleaner doesn't mean you have necessarily fixed an injector problem. Next you should check your distributor cap and rotor for problems, and if you have multiple coils move a different one to supply this cylinder and check the codes again to see if you still have the same problem with the # 6 cylinder. If so, do a compression check when cold for that cylinder ( could be only developing good compression after warming up and expanding things ) and if it's good, then pull the valve cover and check that cylinder for broken valve springs. With the valve cover off turn the engine over without starting and just check and make sure all the valves are moving approx the same, and opening the same distance. If this engine is direct port injection and everything still checks out ok, pull the injector and take it in and have it checked for proper function. Doing these things should help you isolate the problem.and get you back running normal and not setting new codes.
