Cons, besides moisture, header wrap retains too much heat and will make the metal brittle. Over time the header will crack. Why do they use it in racing? Because it does reduce underhood temps and they really don't care about swapping out headers every so often, part of racing. Plus they probably get them for free or close to. Remember what works in racing doesn't always work on the street.

'86 4Runner 5" SAS
'97 4Runner
'05 Corolla
'00 F250 PowerStroke