On the right front cylinder head at number 2, there is the EGR port on the 5.7 which is not on the 6.1. It comes out just if front of the exhaust port in the head and then enters the manifold where it makes a sharp 90* turn into the exhaust runner.
Some people just use the 6.1 gasket and leave it blocked off, but you will get a code showing low EGR flow. Also it runs a little cooler they say with it running so I will make sure it is. I placed the stock gasket over the flange so I could mark out where the extra flange bolts needs to be drilled as well as the position of the EGR port.
The extra flange hole needs to be drilled 11 mm like the others in the flange apart from the slotted one shown. A slot needs to be made from the bigger circle so the EGR can flow into the exhaust primary.
The flange is 3/8" thick so used a die grinder to make a slot just over 3/16" deep
I also cut the gasket to give more area for the gas to flow into the primary as it would no longer act to help seal anyway with the gas running on one side of it and would burn some of it away over time. For final assembly I will use a 2009 5.7 OEM gasket, don't use any thing but OEM, as it has the D shaped ports and the EGR hole and slot already punch in.
A good thing about these headers is that all the lower bolt holes are slotted so I just screwed in the bolts part of the way through the gasket. This helps keep it in place and the header was slipped over the bolts and the rest of the bolts screwed in with my fingers. Having a stand to support the other end of the headers makes it easier too when doing it by yourself.
Can see how the EGR port sits in the head. Very tempted to die grind a slot on this side too, but others have reported it works fine without doing that when using the 6.1 stock manifolds on these. Be very easy to just drill through the port into the EGR port, but don't know where the oil and coolant passageways are and hate to drill through one!
The extra forward hole can be seen here that the 6.1 doesn't have. So remember to take that into account when buying your replacement M8x30x1.25 bolts. You will need a total of 17.
I was happy to see that these headers cleared the bell-housing just fine. When you run the 6.1 stock manifolds on these, the bolt hole protrusion shown here needs to be cut off.
Another side done.