On my 03 with L92 intake, I have one vent from rear of driver side valve cover to the L92 intake. I capped the vent on on the valley cover.

Should I put a small filter on the valley cover vent or keep it capped?

 

no he means the steam vents. You have 1 on each end of the head, so a total of four. early ls1's had them all venting to the radiator. Our trucks usually have the front 2 connected and then going through the TB then to the radiator. The rear 2 are blocked off. You need to vent those rear 2 just like the front 2 or you will get hot spots and could burn up the rear cylinders. That is the reason #7 failures are so prevalent in these motors

 

I don't have 4 on my 03 truck. I have only one on the rear of driver side valve cover which is connected to the L92 intake that I swapped to.

L92 intake/TB do not have any other connections, so, I capped the vent on the front of the valley cover.

 

This is what i'm talking about, the metal tubes that connect each inside corner of the cylinder heads:

 

Stock shortblock?

 

lsx, billet internals. just cracked the lsx block around 1800hp