hi all, newbie on here but have read many posts in the pasts and found you all to be pretty helpful.
i have a 2002 e39 525d and have been looking into the decat idea, i have seen a few different pipes available for a pretty reasonable price but recently i read a post somwhere that said my car may have 4 cats on it, 2 in the downpipe and 2 underneath in the middle section. Ive looked underneath and it would appear to be so... so my question is if i buy a decat pipe for the downpipe will i need to remove the other two aswell to notice any difference?
has anyone done it with or without removing the 2nd set and what was the outcome?
also i have notices on gentle acceleration at around 2000rpm a sort of surging/pulsing, it stops when you accelereate harder tho?
any ideas, suggestions or advice would be great