sl2fast

ok well i had a case of hesitaion, my ses light was on had it scanned o2 sensor was bad, i replaced that the hesitation is still there, but not as badly. when i rev my engine sometimes the rpms drop way below idle then jump back up to normal. could it be a bad fuel filter? bad coils, plug wires? injectors? what, tahts what my haynes guide said it could be but i want to know first hand from u guys b4 i start spending alot of cash. its a 99sl2 with 112000 miles.

__________________
my saturn is slow