Code 44??

My '89 Suburban started acting funny hard to go up hills went as fast as 25 mph. I couldn't speed up when I limp it home. The code was showing 44. It has a new exhaust on it and the o2sensor is new. I had my husband check but we couldn't tell what was wrong.
Can anyone help with this issue?
Thanks!!

44 = Oxygen sensor voltage was under 0.2 volts for 50 seconds of closed loop operation.
(Lean Exhaust Indicated)

44 = Oxygen sensor voltage was under 0.2 volts for 50 seconds of closed loop operation.
(Lean Exhaust Indicated)

Does that mean I need to get a new O2 sensor?
I was trying to eliminate the possibilities what it was. Now all I do is smell fuel when I tried to drive it. If anyone can help i would appreciate it very much.
Thanks.

Matthew,
Thanks for your help. I saw your post for troublecodes.net and use them to get some advice.
Roy from there told me it was a clogged fuel filter.
I also had to change several things before I asked them. Such as my knock sensor, O2 sensor, dist. cap & rotor plus ignition coil. It still registered the lean exhaust until they sent me down the path.
Thanks for all your help.