Driving it off the cliff

[Stl-986]

I get vacuum not building until the rpms increase, makes sense. What doesn't make sense to me is the vacuum dropping so much and so fast after though. It should hold or drop very very slowly right?

[911monty]

Jake Raby has a post somewhere that states there are different modes of failure of the AOS. One is the vacuuming of oil from the crankcase but there is also a mode that causes massive vacuum to the crankcase which can suck the shaft seals in and can cause oil starvation to the oil pump. With the oil pressure dropping low when coming off idle you might want to get a manometer and see what is happening there.