across this site when searching for cats & exhaust threads you'll find posts upon posts stating that Z22SE engines don't like de-cats, as said above its hit & miss weather sport cats can be fitted without EML, 200 cell is the safest way to go after removing the OE one & if your feeling brave then it can be chanced with a 100 cell cat.
as above there is O2 simulators that can be fitted to try and trick the ECU into thinking all is good and poundy has sucsessfully got a de-cat pipe in with no EML on his SC 2.2 vectra.
imo theres not enough back pressure in a N/A Z22SE engine to remove the cat completly and still get positive gains from it unless your main goal is to make noise.