PLEASE HELP-2nd turbo not working
 

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 could take it to Ivan here in Sunnyvale but i'm just trying to prevent another kick in the wallet. I appreciate all the help. Thanks. Em