It's difficult with problems like these, as usually double de-cat doesn't cause problems, but changing the flowof the engine may have made a small not-noticable problem become a big one.
The title is slightly mis-leading, as you say your problem was there and got worst when you removed the cat. maybe best to change this title to NA running rough or something, as it doens't look to be the cats causing the problem.
You have two options to look at first, the fueling or ignition. if you have a friendly mate with a garage maybe check the emissions to see if its over/under fueling. It's not a problem solver, but may help put you in the right direction. Maybe by removing the o2 sensors you have knocked something, or maybe one of these have an issue?