Mild stumbling just under 2k rpm?

[Rich Rich]

I recently failed CA emissions and have changed the following: dist cap/rotor, o2 sensor, plugs & wires, fpr.  I'm still getting this mild stumbling while holding 1800-2000 rpm in 1st gear.  Interesting when the engine is cold it seems to disappear, but once it gets hot, it's rough.  Seems to run fine otherwise, good idle, good boost, about 22mpg, etc.  I have a feeling this is causing my emissions to fail and am trying to get it resolved before I go get a re-test.  Any ideas would be greatly appreciated.

Thanks!!!
200q20v avant 166k