Did you disable the computer controls when you swapped carbs or did you
put in an electronic carb?  Most folks go with a normal Weber when they
replace the Weber-Carter BBD that was in there.

If not, the computer has now gone into 'limp home' mode which clamps
down on the timing and basically shuts off all the anti pollution
controls.  The O2 sensor only works on/with an electronic carb.

When you disable the computer and manually set up the mix and timing,
you can get good numbers for emissions.  I still have the BBD, but
manually set for mix and timing with no computer and no cat because my
CJ7 doesn't require the cat here in Canada and I still passed emissions
with nice numbers.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)

Weber also gives instructions on tuning the carb with a 4-gas analyzer;
probably the only way to do it if you need to meet emissions.