TBI regulator rattle?
My father has a '90 chevy pickup with a 350 and TBI. There is a new rattle sound coming from the TBI. The rattle does increase and decrease with engine rpm. It sounds like it's coming from the fuel pressure regulator. It's always noticeable on idle and goes away above 2000 rpm. He's changed the regulator but it did not change anything. If he disconnects either injector, the sound is still there. The truck is running perfectly, it's just this rattling sound that's puzzling.
Has anybody encountered this before? Any ideas? Could the regulator be fine but rattling as a symptom of some other problem?