I have just installed a used procharger M-1 on a 7.4 MPI and it makes noise @ idle. I have read threads stating that prochargers do make noise. The noise goes away off idle, I assume as pressure against the turbine blades becomes greater. The previous owner suggested the use of straight 40 wt oil. Any suggestions?

Mine sorta has a ringing sound like gear noise,you would think the bearings or gears were going out of it but it's been doing it for 4 years since new,Smitty

Mine did it, really worried me, but is the norm. Mine either got quieter, or I didn't notice it as much after several uses.

Most that I have seen do.

My brand new ones do. At least with the hatch up I can hear it. I am told that you should only use procharger oil, looks thinner then 40 wt to me.
100 hours between changes. I would buy the right stuff.