I'm having this same problem as Yotsuya.
His description matches mine exactly. At idle, it hovers around 700 rpm, but is not smooth at all. Whenever at low RPMs, there is definite heitation, in almost any gear, up until 1800 RPMs, from there and up, it seems normal.
So for instance, when doing a rolling stop at a stop sign, put it in 2nd gear, and there is definite hesitation until the revs come up.
Has anyone found a solution to this?
(Just tonight, I took out the 2nd filter, started it back up again, and engine died. Put the 2nd air filter back - the one right before the throttle body - and the hesitation was worse.... the revs would drop so low, that the engine would sometimes die. i drove around, and it seemed to get better. the low RPM hesitation was gone, and when I would stop at a stop light, the RPMs remained steady at around 700)