Vaccum Diagram for 2003 Chevy Blazer
 

Does anyone have a vaccum Diagram that includes the line that comes out of the Driverside fender?

Try a search in the forum and have a look at the DIY sections and the tech articles.

There is a vacuum reserve tank inside the fender that line hooks to. This tees with a plastic line that goes through the firewall under the brake booster, and through a check valve to vacuum source on the intake. Somewhere in this same immediate area this also splits off to be the vacuum supply to lock the front axle into 4WD operation. Depending which year and type of transfer case you have, this goes either to a valve on the transfer case or to an electronic valve on the firewall above the distributor.

Hoses are 7/32 and 5/32. In a 2wd their only function is to open the doors for the HVAC. IMO check valve is not vital. If the hoses are open there will likely be a vacuum leak to the intake. Here are some pics from a 2wd: https://blazerforum.com/forum/2nd-ge...d-hose-102386/