Having a strange issue when driving in wet conditions usually starts when I hit a patch of water on the road. Get a very loud resonating sound that suddenly starts almost like a tyre rubbing against the arch, it's not this however as when I pop it out of gear it stops, and the noise increases with revs, it doesn't last long (5 minutes has been the longest) then fades away, and have noticed it doesn't happen as much when the engine has warmed up. I'm thinking it has something to do with the exhaust however I don't understand as it doesn't happen in dry condition it has a custom emp on standard manifold. Anyone had a similar issue?