Thanks for the pics! So you blocked off the hole on the side and are just pulling through the hole you made in the front? There's no advantage to opening the hole in the fender and pulling through the fender?
The foam strip runs vertical from the bottom rear corner of the air box to the top rear corner of the air box... then along the top/passenger side of the air box to the front... then it goes across the front of the air box-- along the seam where the top and bottom of the air box join-- just about half the length of the air box to where the radiator support is... then it is folded in half to create a thicker foam... the thicker foam runs down between the radiator support and the bottom portion of the air box...
This isolates (to a degree) the radiator fan wash from the intake... you have created a barrier along the top/sides of the air box... the air box can still pull some air from between the air box and the fender (from below)... the triangle hole kinda makes up for the restriction created by the foam (the air box can no longer pull (hot) air from around the top of the air box with the foam in place)
Don't remove the 'tape' from the hole in the fender... it was discovered by GM to cause water ingestion in the earlier Duramax models... that's why the tape is there...
It took me longer to type this than it actually takes to run that foam around the air box... I pulled to top of the air box off and removed the filter... that way I could position the foam where it needed to be...