1994 S0 Blazer 4x4 4.3 CPI... After changing the plugs I discovered a vac line broken from age that leads to somewhere near the firewall on the passenger side . It heads towards the front along the fenderwell and curves under the battery box to what I believe is a canister. Any ideas on where the broken end connects to? BTW, All hoses at the tee behind the intake are connected. Mileage has dropped to 14 mpg

 

If its going under the battery, thats where the 4wheel drive vacuum actuator is.

 

Any idea where the opposite end connects?

 

If it's the one to the actuator the other end connects to the vacuum switch on the transfer case.

 

If it's the 4wd line, it will follow the transmission dipstick down to the transfer case top. It can be a challenge to get to, but you should be able to trace it back from the switch by feel.