Don't know what's going on with the throttle body adapters, seem to have been a rash of them lately.
Even when ordering new ones some are having them split.
I've owned 4 pre '08 models and only had to replace one and that was on a Hammer that had sat covered on a carport for 5 years. Replaced another on an acquaintance's bike a few years ago and it's doing fine.
As to why the carbon build up I've no idea.
What I have done to ALL my Vics is reroute the crank case vent hose to the ground and use a K&N filter to prevent dirt build up. Not that it would get in the engine just keeps the residue from the oil mist off the bike.
I started doing this with my Harleys back when they started venting the crank case into their airbox.
I just don't need an oil mist going into my intake.

 

Vent hose added to the list for winter.

 

Well I might be a fault on the boot who knows.
I am going to try a temporary modification. I have used some hose that is just barely bigger than the boot. Slid it over tge boot and the intake tubes.
clamp on both top and bottom.
it seems a little more ridged.
the air box does sit a little higher as well.
we will see how this works. Maybe a new method to run with. I am most definitely going to be putting a crank breather on the winter as well