so yeah, i've noticed that the past week my car has been running a w/ a noticable lack of power over the past week.

it just is being really slow, i know it's a four, but yeah- it usually feels a lot more powerful. any suggestions on what i should do to help this out? im changing the air filter tommrow, it really needs a change, the oil was recently changed, plugs fairly new. so i think a tune up is out of the question. any suggestions??
thanks