I have heard mixed information on if a flash can cause damage to your car. What are the negatives to flashing your car and why are there so many problem with the 2005 mustang and reconfiguring the computer? Also, does anybody know what most dealer's policy is on headers and warranty.

 

Ask your dealer about headers, its up to them if they want to be ****** or not, but they should be ok, since letting air flow more smoothly out shouldn't affect anything on your engine.

 

The only way a computer flash could damage anything is if you flashed the computer with the wrong program. For example if you tell the computer to lean the mixture too much or advance the timing too far you could damage the engine. As long as you are using the right tune for whatever changes you made you will not damage anything.
In regards to headers or any other mod, as long as the failure can't be linked to the aftermarket parts you installed your warranty will not be effected. That's been stated on this board a million times and my dealer confirmed that as well.