Engine Not Steady Idling Between 2000 & 2500 Rpm

[lexamainia]

hey guys, thanx in advance for looking at my post i have had a cel light on with code 25 which is offcourse lean air fuel so changed two o2 sensors before the cats which eliminated the check engine light and the cars been running smooth ever since till yesterday, (now i am having a problem between 2000 to 2500 rpm) engines rpm fluctuate now,they drop down to 1000 and then come back up and thats when i am just idling the engine at 2500rpm, and when i am driving at about 45m/hr with approx 2000 rpm engine feels like got held up rpm would drop for few seconds and rev back up. i kno we got got all the pros in here so any advise to put me in the rite direction would be really appreciated. thanx again :cries: