Check engine light on and very sluggish

2001 Impala LS with the 3.8

So I found a vacuum leak and now the car is back to a normal idle. Thanks again for all the input from my other thread!

Now, after taking the car out for a test drive, the CEL light is on and it is very sluggish when I give it gas. The code from autosone shows the o2 sensor... Would that cause it to be that sluggish? and even casue it to shift from 1st to 2nd gear sluggishly? (If that is even a word!)

I already have a stock downpipe and Cat from my 2001 grand prix that is an exact fit, and figured I would replace the O2 while I swap that out. Is there anything else I should be looking at??? Again, the MAF sensor was already replaced about a month before it started acting up...

Thanks again guys!

you may have a bad catalytic converter. GM extended the converter warranty on 01-02 GM W-bodies and Impalas due to a known issue with the sustrate breaking off and clogging the exhaust. The warranty extension has been revised more than once, so call your local GM dealer and see if you may still be covered.

Replaced the Cat and the upstream o2 sensor... car runs like new! It is amazing that a plugged Cat can make the car run that bad!

Word to the wise... my Cat was plugged so bad that the car would not go over 25mph. I found out the hard way that trying to drive it like this over to my friends garage was a VERY bad idea. The heat that the this produced actually melted a small hole on the air intake manifold. I was able to use some of the plastic mold and some jb weld to seal it up. This repair was much more involved than the Cat and o2 sensor replacement...

Thanks to everyone who helped me diagnose the problem.