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...
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On my previous golf tdi I found a wire mesh inside the canister....
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So I had to cut the canister right out of the downpipe, remove the ceramic type of cat and weld it all back up...
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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.