LizardKing, first off, don't try and convince KirkyG, he is an opinionated, know-it-all, who doesn't take the time to learn anything before running his fingers on a keyboard.
KirkyG, please don't respond.
I have been leasing cars/trucks for 30 years and know the benifits and dissadvantages very well. There are many instances that leasing is quite adventageous and others it does not make sense. Do what you think is best for yourself, and don't argue with people.
Back to your problem, what reason was given for Ford to come out and look at your car in the first place? Normally, the service department makes the initial call whether to perform warranty work or not, not Ford. If the dealer decides not to do the work, this is when Ford steps in and backs up the dealer, unless there is a catastrophic failure.
There only two reasons I can see Ford giving you a hard time, is they do not want to remove your exhaust system to do the work, seeing they will be held responsible for it if there is damage during removal and re-install or re-installing it incorrectly. The other reason might be the Ford Credit issue, seeing they are the legal owner of the vehicle and do not feel they gave you the right to mod the car in any way.
I thinks Mr. Jason Keay is blowing smoke up your backside. He knows more then he is saying.