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!

 

Kooks performance cats. Boost will drop but power will be th same, boost is just measure of restriction, less restriction less boost and more power...

 

Your best bet is to get high flow cats like smokinlmm mentioned


Torqstorm