Your dealer is correct, FMC will not warranty the engine with aftermarket power add ons, ie "tuners & chips". If you get out your warranty manual it specifically states that "tuners & chips" will void the powertrain warranty. Sorry but FMC will win this battle if you take them to court, and it will drag out for 2-3 years, in the mean time you will not have the use of your truck as it will be impounded for evidence and you will be paying your attorny alot of money for nothing.

This falls under the addage of if you are going to play then you are going to pay.

Since you are going to be paying for the repairs out of your pocket, you want to install ARP head studs and Hypermax gaskets since you tow heavy with a tuner these are a good upgrade when modifying the Hp & Torque of the 6.0. Also the Banks Six Gun is notorious for lifting head gaskets on the 6.0 and trashing Torqushift transmissions.