The elbows make a neater install - but they aren't required - if you go with 1 piece hoses make sure you don't kink them in the bends or when you put the engine cover on (if you put the engine cover on) - blocked hoses are bad - I don't remember the error - but it will cause a problem.
(most of the hoses are 3/4" and the Provent is 1" openings so you do need reducers)
If everything is routed right it doesn't really have room to move - so ties may be overkill - but they might help with keeping the tubing bends routed correctly, so they won't hurt.
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2005 CRD
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