I know this is an old thread, but I think it's the best place to ask this particular question with all the information already here.

I was planning on separating the two systems myself and did some research on how modern cooling systems operate and the purpose for a overflow/surge tank was.

I found it is simply an extension of the engine cooling system and gives air space for fluid expansion during higher operating temperatures. This holds true for the "Charge Air Cooling System" or Inter Cooler system.

My question is this. If I leave the OEM tank and block the Inter Cooler port on the bottom or replace it with a Standard/Limited Crossfire OEM tank without the extra bung. Could I simply add a smaller additional tank and route the two lines to it with an appropriate pressure cap, thus isolating the Inter Cooler system and giving that system it's own tank. I was thinking 7lbs for the cap as it should never even get close to boiling anyway.

I am including diagrams based both on those presented above AND actual viewing of the engine bay. The OEM diagram is as accurate as I can make it. As to the modification diagram, it may seem a bit more cluttered, but that is to retain the OEM tank and plumbing and only move TWO hoses and replace one 3/8" tee fitting with a straight fitting.

Comments? Advice? Good idea? Am I crazy? (I lean toward the latter... )

Yep, I use Visio for LOTS of stuff...