Bowzer and others have a damn good point here. Only YOU can say if this is out of line or not. Go with your gut.......there are other dealers than the one you bought it from, which sounded to me like a used car dealer not a Honda dealer. If it's enough of a problem that you feel there is a need to pursue it then do so. After reading and re-reading your posts it's possible that the rough idle is more than the norm and requires that something be done/corrected.
I still think this is worth a shot though, enough for 20 gallons not 12. Pep Boys, Wal-Mart, Auto Parts stores all have it. Can't find the 20 gallon size? Buy two 12 gallon treatments and use 2/3 of the second bottle. Put the final 1/3 in your next tank. It cannot harm and has cured idle problems for me before in other vehicles.
