slight vibration

I bought a used 2002 Lancer OZ 5-speed back in January, it now has close to 40,000 miles on it and I recently took it to the Mitsu dealership to have the oil changed and tires rotated.

I am very please with this car, it's a nice car and I got a good deal on it I believe. My main concern is that there is a slight vibration when the engine is idling. More noticable in traffic conditions or when I pull up to a stop sign or red light. As far as parts, everything is factory as I see it, no modifications have been done yet.

Can anyone recommend a solution to fixing this vibration?
Should I get it looked at? Or replace an air filter or something?

Also, has anyone noticed the OZ after starting revs up by itself and after 5-10 minutes the revs return to normal, i.e under 1000rpm??

2 weeks and no replies to my post, wow! That's real helpful, thanks.

Being as how I don't know much of anything about the mechanics of the Lancer I thought someone might have an idea.

Anybody?

Id get it checked out if I were you

my car (2k2 lancer ES) has the same revving "problem" , it starts out normal, then goes up to 2000-2500 rpm? then drops back to normal after 3-6 minutes , if so my tech said its normal, its the engine trying to warm up and get oil circulating , usually does it more when very cold.

I used to have that problem, maybe you idle control switch (not sure if thats the correct term) has gone or is on its final leg.
Either that or your revs might need adjusting.

ragin