I’d compare it maybe a rock in a metal can. The rattle intervals increase and decrease with rpm. My shop just said to drive it. They said they’ve seen people drive with the rattle for over 100,000 miles. It’s just strange to me because the car ran great (only 138000mi) and then it randomly started. Only thing I can think of that triggered it was that I drove through a puddle not seconds before it started rattling. This was a relatively small puddle, so I can’t imagine any water would have reached the intake.
As for throttling it when the brakes engaged, I have not tried to reproduce the sound that way yet.
Thanks guys