I just used a piece of heater hose and it works fine too. Anything with the right ID will work. I think they used the foam because it had so little mass that it would not influence the temperature of the air going through it but I never had any trouble with the heater hose so I don't think it is too critical.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz