I had done this mod to my previous golf tdi with good results so I found the time today to do it on the mk5
I wasn't expecting to find a cat type ceramic material when I opened up the downpipe canister but this is what I found...
On my previous golf tdi I found a wire mesh inside the canister....
So I had to cut the canister right out of the downpipe, remove the ceramic type of cat and weld it all back up...
I'm chuffed with the result as the spool is now noticeably sooner and low down it seems more willing to get going. There's a slight increase in turbo sound which is nice.
I haven't driven far enough yet to gauge any difference in MPG.
It's a dirty job cutting the can open so use a mask and obviously only attempt it if your handy with a welder.