"Hello" and Welcome
tech questions best asked in "Omega help" as more of "them that know" read there than here ..
But the 2.6/3.2 all have 4 sensors and 4 cats. 2 "little" cats and 2 "main" ones, 1 of each in each downpipe. The sensors are either side of the little "pre-cats" and can give "false" readings quite frequently.
Moving the 2nd sensor to after the main cat is one fix, another is to do a couple of tankfulls of premium fuel - esso, shell - rather than supermarket stuff as this can often "cure" the problem for a while.
You can do your own diagnostic check with the "pedal trick"
http://www.omegaowners.com/forum/YaBB.pl?num=1189022687expect an 0420 and/or an 0430 error code.
Personally, when I get one of those I use my code reader to clear the fault and reset the light .. it usually stays out for about a year ..