Just to update on this thread and finish the tale.
Had the O2 sensor refitted today at Thor, new flange welded on etc.
Result? Fueling was fine on the dyno and now putting out @ 1.2bar 349.7 (ok ok call it 350!) BHP and 358.3 lb/ft at the hubs with good curves
Thats 18 bhp and 11 lb/ft more at peak and with stronger overall curves throughout the rev range than before... Now thats more like it, moral of the story is 'never underestimate the power of a single sensor!'
Bit confused why it originally made 344bhp 354lb/ft with the standard exhaust/cat on still though, hardly gained anything with the Nur and 2nd decat compared to those initial figures I hit bang on 1.2 bar this time whereas last time it was 1.24, could the extra .4bar have given a few extra horses and lb/ft making the gains this time seem smaller? What ya reckon