What are these holes for, should I block them off or run them to connect to anything?

 

I have a US EvO9, so my vacuum lines are likely different than the EvO 8

Heres our US schematic for the emission control lines. If your throttle body ports are open, they certainly need to be corrected

 

USDM Evo 8 same lines connected the same way. Obviously these are vacuum ports that suck in unfiltered air. Just how much or what sort of porting they connect to and what effect it will have on idle if plugged - dunno.

 

Other market evo's (I think) don't have an EGR system, so they don't have those tubes there. I'm pretty sure those holes aren't drilled through on OP's car.

 

Simple enough to tell, stick your finger over the port while the engine is running and work the throttle.

 

i would agree with letsgethisdone

 

I can confirm JDM and ADM both have EGR. As mentioned put your finger on them to check if you need to block them.

 

I doubt theyre are open ports.