I have a VR 93 FD. I just found out via my turbo boost gauge that my second turbo is not kicking in after the first one engages. I know that the pattern should be close to 10-8-10 but it's like 10-8-4. everything is stock except dp, aluminum ast. I'm checking the vacuum lines but are there any other possibilities? I appreciate all the help. Thanks. Em

 

Maybe you should post in the 3rd gen section ?

 

To the 3rd gen section it goes

 

Look under the hood at the one way valves (green and black) they are attached to the vacuum lines in front of the intake manifold. They have an arrow on the side so remember which way it points. It is either one of the two valves which has gone bad or you have a bad hose (came off or leaks).