Is the exhaust pipe diameter on my '04 5.4 2.5"? If so , I know what muffler I want, but I measured the diameter of the stock exhaust at the tip and it measures 2.75" o.d. Is it just this dia. at the end where it turns? I want to add a magnaflow tip but not sure which one to order

 

i think your stock exhaust system is 2.5" up to the muffler, then the muffler outlet is 2.75".

 

The tailpipe is 2.75". You could go with a 2.5" inlet tip since the tailpipe is way past the muffler, I wouldn't worry about any performance issues, 2.5" inlet has a hell of alot more selections out there anyways.