has my cat collapsed?

[lel]

My 1.7 Puma has lately lost power, developed a rattle and has started coughing and spluttering at higher revs. When it started i had a whispy air noise, sounded a bit like a blown manifold gasket but it was alright, then the rattle started then the loss of power.

The car drives fine at lower speeds apart from the rattle but once you try and open it up the video shows what happens, sort of feels like fuel starvation.

I've had it plugged into live data to check the 02 sensors, No1 is jumping from lean to rich as normal and No2 is doing the same, which i believe it shouldn't?

video: https://youtu.be/gqqzSCCUyWY?t=1m2s

[lel]

update:

checked the second lambda and it was jumping all over the place, pulled the cat off and hollowed it out and the car is a little rocket now, much better.