Common causes for low vacumm

[obx tsi]

What are some common, if any, causes for low vac. other than the obvious such as a vac line leak? I have been over the vac lines and can find no reason why my idle vac is about 14-15"hg. As I am at sea level I know it should be higher. Any thoughts would be appreciated. Thanks.

 

[Mr Peepers]

Compression, cams/valve timing are some common ones.

 

[obx tsi]

When I changed my turbo, that I thought was blowing oil, I did see where oil had been coming from the passenger side exhaust opening. Maybe a bad valve seal? Thanks for the info.