I used 2 bottles of genuine Honda MTF II (green label one), and the shifting felt so much better after that.
I would recommend you to change the spark plugs too as in my case
it made a tremendous improvement of almost 20hp!! :shock:
I now it sounds crazy But I have a dyno run to prove.
My car had around 18k on the ODO when it came from Japan and when I took out the plugs they had a little rust, perhaps mine was parked a lot of time, don't know.
I also changed the filter with a K&N drop in, so that might helped a bit in the crazy jump in horse power figures I got.
It landed 162whp exactly as it came from Japan and after the maintenance (like a week or two later) the HP figures jumped to 181whp
these runs where made in the same dynojet of course since they were made on diferent days, air temp, humidity and such were diferent but you get the point.