I currently have just the resonator delete on mine, will be doing a secondary cat delete soon, it's on my menu of things to do list and looking forward to that.
Interestingly h pipe configuration is just before the secondary cats on the w211 e63, which I think it would be the same on the e55. I was inspecting the pipes thinking I could just gut the cats out with a long rod but it's way too deep to reach with the rods especially with the kinks. Best to leave it to professionals and do a straight pipe, they'll do a neat job and hassle free.
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