Interesting. I didnt remove that heatshield on the driveshaft when i did my cat, but no amount of pulling/twisting would get the cat clear of the car. It seemed that the cat would either get wedged between the chassis and turbo, or against the head.
Perhaps with that shield out the way it would have come out some more, but i ended pushing the cat back down as far as i could in the engine bay, and cutting the front pipe with the grinder. Then pulling the cat and stub of the downpipe out the top and the rest out from under the car.
I guess your way would be better if your planning on keeping the front pipe intact though!
Well i took the grinder to the front pipe, not the cat, as i was changing it anyway as the flexi was shot.
Plus i was replacing a (unbeknown to me) gutted cat with a real one for the MOT. The amount of hassle it caused i really wouldn't think it was worth swapping it out every year come MOT, even though it did give a bit more performance with the gutted cat on there.
What i'd probably do, is get a universal 100 or 200 cell cat, and fit it underneath the car using some of audis finest dual clamps. Those things are awesome and would make swapping the cat out and back a piece of cake! Would justt need to have a section of pipe the same length as the cat to swap it over. Or just keep the 100cell item in there and be a hippy