weight aside, the argument becomes where the remaining cats are located for best performance - on the headers or on the mid-pipes. porsche and cost say delete the cat on the headers.
changing mid-pipes is easier; no potential seized bolts in the block, no sensors to deal with. however, here are some links to three easy ways to fix the cel issue:
http://forums.evolutionm.net/evo-how-requests-questions-tips/215795-5-o2-cheater-non-fouler-how.html
http://www.fvd.de/us/en/Porsche-0/-/-/-/item/item_details/VID_33179399-VCD_85527367-gid_29-sort_4-display_50-item_FVD111LAMVER/EXHAUST_-_Tuning_-_Catalytics-FVD111LAMVER-Oxygen_Sensor_Extension.html
http://www.audiworld.com/tech/eng53.shtml
otherwise, everything i find on the intraweb says that the pre-cats are more restrictive than the main cats ...