Yer but where exactly do you mean grab it Duncan?
Ive got new tensioner bearings (i run two on the 3Lt) and a new belt (although it is the rb30det belt) and it has a whoop whopp noise as well. Most nticable on cold starts, but there some other times as well.
Ive heard of a few rb25's that have the same thing, but the weird thing is nothing is wrong -they are all tensioned and setup properly, just noisy.