check your exhaust downpipe, before the cat there is a metal honeycomb thing that sits at the top of downpipe, it may have come lose and blocked your exhaust on the bend before the first O2 sensor
i've just done mine this morning, wouldnt go above 3000rpm, no power, whistling noise when accelerating with foot to floor, mainly in 1st and 2nd gears
also check all vacum pipes