99 cav seems starved for gas?

Okay, so I have a 99 cavalier, 2.2l. It gets sluggish when I try to accelorate. Mostly in 2nd gear but I can tell that it happens in all of them. I was thinking it was my fuel pump, or fuel filter...

Oh, as a side note, I did run out of fuel a few weeks ago, which I know is really bad, but I put an STP fuel treatment in after the problem started to get worse.

I will be performing a major tune up in a few weeks, I would really like to fix this problem at the same time... It is freakin me out...

Thanks.