Posting here first cause I'm a iddy biddy part of this group (secretly hoping you guys can answer me question) but will also post it else where.

Okay, did the research and looked through as many threads as I could stand BUT still came up with no definative answers. Here's the question.

I understand as long as you can prove the part you installed had no impact on the part that's screwed up, the dealer is, by law, required to honor warranty issues...however after reading this particular post, some guy chimes in with another post and says don't mess with the cats or headers and the was the end of the thread. Well which is it?

If I install the headers or cats I want, will it void the powertrain warranty?

On the issue of high flow cats. Because I want to be thourough and do a complete job and not just put on a cat back job, my goal was to totally revamp the exhaust system (long-tube headers, high flow cats, muffler, and larger pipes). I have read the Ford cats are already high flow and others were sure that they were not. What, I ask you, is the truth?

Again, after much reading. I am left with the conclusion that if these mods will NOT void the warranty, they will be emmisions legal? Am I correct in the assumption (provided I buy parts that claim "50 state" legality)?