I switched to the Bosch after I started having trouble with the new black M1 filters. I had been using the old grey ones & I had good readings on the gauge and very slight chain rattle upon cold start up. On warm or hot restarts there was almost no chain rattle.
My first oil change for the start of the summer the A/Z by me had the new black M1's so that's what I bought. Major chain rattle on cold start up, minor rattle on warm/hot restarts and an alarmingly long time to have O/Pres show up on the gauge. I was very concerned that my O/Pump was quitting on me. I bought another black M1 & tried it and had the same results....now I was scared!
Came home(here to our home) and looked around & read the newsletter at the netreg site and decided that I was having some bad luck with the new black M1's. I was going to order another O/P sending unit but buying a Bosch O/F was quicker. All I can say is using the Bosch instead of the black M1 my "noises" at cold start & warm/hot restarts are back to what they used to be when I was using the grey M1's. Quick rise of O/P @ start up on the gauge and very little chain rattle @ cold start. My 90 always had about 3 seconds of chain rattle at cold start as I doubt the original owner ever complained enough while under warr for the dealer to replace the right side guide? Anyway, it always had about 3 seconds of rattle after sitting a week. Warm &/or hot restarts had practically no rattle and the O/P gauge always showed a quick (you almost didn't notice a wait for O/P) build to operating oil pressure.
I guess the A/Z where I buy M1's got a bad batch??? The grey ones worked fine, it's the black ones I had bad luck with so now it's Bosch for my Z! I know that this is unscientific but the nosies & time to build O/P were giving me nightmares!
Tom