Only real problem with what you are wanting to do is that you are putting WAY too much stock in MP crap. This site and others has so much more and better info, I can't figure out why you are still looking at their stuff for anything other than a laugh.

Seriously, several guys have posted exact part numbers and experiences- that is worth far more than MP telling you what THEY think will work for YOU, and conveinently they make those very things...

I also don't think the 3" exhaust will be worth the money spent with manifolds. Extude honing would help but for the $$$$$ you could just run some NICE headers, see better gains overall(except nonstock looks) and be done with it.