Engine Stutter

I have a 2003 TL-S. Runs fine most of the time. Every so often, while cruising at a constant speed, does matter what speed, the rpm's start fluctuating and engine looses power. Kind of stumbleing. As soon as I hit the gas, the rpms stablize and the engine returns to normal.
Does it when wet, when dry, cold or warm.
Anybody have any ideas? Thanks.

i take it you mean "Doesn't Matter what speed" but if you at a cruise...could be an IAC problem, a vacuum leak wouldn't make a diffrence off idle, unless this was a big vauum leak, in that case im pretty sure you would hear it...and it would stall at idle, no CEL illuminated??

Yeah, meant 'doesn't matter what speed'. I haven't noticed anything like a vacuum leak under the hood and idle runs just fine. No check engine light. Can you define IAC? Ignition coil?
It happens normally when I am at constant throttle position. The power fades and the rpm's begin to droop. The tach will jump a little and the longer I let it go, the more the power drops. But as soon as I hit the throttle the system stableizes.:screwy:
Could it be the throttle position sensor?

Appreciate the help.

IAC = Idle Air Control, even though your off idle...your IAC Opens up to around 100%, sometimes if it doesn't open you can feel a slight sputter. It could be your TPS, you can always check it before gettin to indepth.