cel p1399, jerking at 60mph

[kyleb4u]

I have a 2000 Honda Accord V6 EX Coupe, with 168K miless on it, ran perfectly 2 months (2k miles) ago. I've been having this problem lately with my car. I can't seem to figure it out. my car runs perfectly except for this "front and back" motion, like missing, at above 50mph and only at or below 2000rpm. i noticed that i can very lightly push the pedal down and it feels like that throttle is opening, but the rpms stay the saem at about 1800rpm. ten i push it alitle more and it JUMPS to about 2200rpm and stops jerking. I can't figure out what this problem is. but my car doesn't miss at idle or at any other time. i got my codes pulled on my car today and i'm getting p1399, plus the ther p0300 and p0301-p0306. there is no way my car is missing on all 6 cylinders. i had it down to just p1399 coming up on my diagnosis after i changed the plugs. but now. 2 days later and 2 cold starts later. I get all the same codes again. I honestly dunno what the problem is. i do know my valves aren't tapping, my fuel/air ratio is fine (my plugs are burning right, light brown/reddish color), my tranny is fine, i dunno about my egr valve. i unplugged the vacuum line to see if that was the problem, but it made no difference, still does that jerking at above 50mph,below 2000rpm. i'm running out of things to do. the egr valve is $72 to replace, i'm not spending that unless i have to. i certainly want my car to run like it use to. Honda dealer wants $80-$108 to just diagnosis it. One other thing, for awhile it ran terrible, and missed when it was cold fairly bad. it started this like a month ago after using wal-mart gas for 2 months. so i finally switched to shell, threw in some lucas octane booster, and iso-heet to clean it up, then changed the plugs and now it runs great. except for my cel and that missing (?) i am describing, which was already there. i am desperate to get my car to running better again. the egr port has been cleaned before along with a valve adjustment at 110k miles. plez help!

[Kastigir]

I'm getting nothing for a 1399, but other codes in the 1300 range have to do with the cylinder position sensor. If it's failing your car will indeed misfire on all 6 cylinders.