PerformanceTrucks.net Forums - Supercharger and cats

I have a 2005 F150 FX4 supercrew with 6inch lift and 35"BFGs. I have a new 5.4 from Promar and a Edelbrock Supercharger. I have a small exhaust leak where exhaust pipe hooks up to exhaust manifold. This is due to a new set of headers I put on when installing engine. Headers were warped and leaking at collectors. I now have new stock manifolds on now but my exhaust pipe is egg shaped now and will not seal up. I have been to several muffler shops but cant get exhaust to seal up. I still have stock cats on that have about 230000 miles on them. My issue is which cats do I need to install. Ford wants about 2800 for new cats and I think that's a little too high priced. I have talked to many people and look at a lot of sites and I am getting all sorts of ideas. I have been told that if I go with a free flowing cat my boost will drop so I need some that are close to stock as possible. Borla,Flowmaster,and Magnaflow have come up. Any suggestions would be appreciated!