Just went through this with my '01 SS. Cat was clogged. Mine fell apart quickly inside and had a dramatic loss in acceleration and threw the misfire code. A new cat fixed it. Just a thought.

 

So thought I should post and say I finally found the root of my issue and that was coils and icm needed to be replaced. Did that today and my monte is running beautifully with all the power you could ask for Thanks all for your input