Have a question as I stumbled across something last night. My LS6 intake had a vacuum port at the back of the manifold where I would attach a small vacuum line that runs into the main harness area, however the LS3 does not have this provision. Actually, it looks like it is in fact molded with a vacuum port and it is capped/plugged and I really don't want to break the port off altogether trying to open it if it isn't supposed to be. Any ideas??

 

Did you get it figured out?

 

No not exactly, I'm just running an extended vacuum line off the front of the intake manifold to the back.

 

The rear of the LS3 has the small vacuum port next to the brake booster port. You just have to twist the tab off and its good to go. Might have to run a small drill bit through it to open the hole up.

 

Yea that's what I was wondering if that's removable.. thanks!

 

That's what it's for, it's just not used in some applications, GM does that a lot with plastic parts, lets them use the same part for multiple things.

 

IIRC that is for the heater core A/C. When I ditched the core in the firewall I had to pull that back off the rear of the LS3 manifold and vacuum cap it. The line is bundled into the harness right next to the PCM.

 

Yep that's the one!