Do you mean the ribbed hose that takes the air from the area above the radiator to the airbox intake? I have seen this hose folded inward a bit at the radiator on several roadsters. One of my future projects will be to replace it with something smoother and possibly to a cooler area. But if it is this hose you talk about I am amazed that it caused a high iddle.
At iddle there is soo litle air required, a slight restriction in the intake should not make a difference.
I know what you mean with the rev-hang at high rpm, anoying, but as you say many engines of many brands do this.
Its caused by the pollution control gizmo's (EGR/IACV).
Cheers J
