When you install these headers get rid of as many brackets as you can, they are useless.

Also Bolt the rear head on fully then do the front. If the front will not sit flat against the head, don't force it, you will break a header stud. Instead take the crossover pipe and trim a 1/2" at a time off the piece that connects to the rear header and a 1/2" off the front header, takes some work but eventually you will get it to sit flat and perfect.

Also get these clamps (napa sells them too btw for $11 which is cheap)
ZZ Performance

You need them for the crossover pipe the stuff they give you is junk.

Get some RTV copper gasket stuff too.

and get a new 2.5" downpipe to catback gasket...otherwise it will leak. If you've never taken it off then it will definitely need to be replaced

and If I were you, I would block off the EGR, its useless and so much better not having it there, just get a boxtune pcm and have the code deleted. Or don't its up to you.