My rabbit started the same thing from idle up to about 2000rpm only since I put a new injector pump on. It's kinda a low pitch rattle and if I push or pull on the intake snorkel it stops, so like you I put a piece of foam tape on the belt cover were the snorkel rests. It didn't fix a thing.
Maybe try removing your snorkel and see if anything changes, if you take the cover off does it still do it? Good luck!!
Nothing changes when removing the snorkel. Thr only thing that makes it stop is applying pressure to the cover with my finger.
I'm going to drive it around with the cover off Wednesday and make sure it goes away.
I decided to try insulating the cover with more rubber and some nylon washers at all mounting points.
It did reduce the rattle from migraine-inducing to mildly irritating. I may just leave it the way it is.
How risky is it to drive with the cover off? Its dry here in Arizona now, but it rains pretty heavy in the summer.
I've heard of rocks getting in the belt and making it jump tooth.
I've seen plastic bags being sucked up and ruining the engine