Just recently started to hear a rattle between 1500-2000 RPM on my 91 with 95K miles. I took it to Shad at Driving Ambition, and he suspected this could be the cause.
I stopped driving the car, and I will be removing the intake in a couple of days to take a look. I'll let you guys know what I find. In my opinion, this few hour inspection is a small price to pay to prevent engine failure.