[Christ]

Aye, according to every Honda Technician I know, they all hated the lean burn setup for only one reason - it's not very "smooth" in transition... the Honda ECU doesn't slowly lower the AFR, it literally just drops the fuel ratio under the curve when the input is correct to enter lean mode.

So you might be cruising along, and lift your foot off the pedal slightly, and all of a sudden, you're in lean mode, and you feel a 'burp' in the otherwise smooth operation of your engine... what's actually happened is that while you were cruising along, you were probably maintaining an AFR close to 14-15:1... all of a sudden, the stars aligned with the moon, Saturn entered it's third phase, and Jupiter got rings, and your AFR dropped down to something closer to 17-20:1 (if I remember correctly).

So what actually happened? Ever get an air bubble in the carb bowl while tuning a carb'd car? When that happens, you get a 'burp' from the engine... one or two cylinders don't fire for a cycle. Bam - there's your explanation.

If you're absolutely bothered by it, you could try a few things, like softer motor mounts, or making sure that all of yours are perfect and that your engine is aligned correctly (there is some play in the mounts of most Hondas, which allows you to re-align the engine slightly.)

The softer your mounts are, the less feedback you get from the engine when it makes funny and does things you don't think it should be doing.