I have a 2005 F-250 with the 5.4 and added maggie high flows about 50,000miles ago. I now have these codes thrown on the factory tune and my 93 Troyer tunes. Do I need new cats or would you start with the O2 sensors?

 

The O2 sensors are doing their job, don't replace them. It's telling you that your cats are failing the efficiency tests.

 

That's what I as thinking. Would this cause milage to drop about 2 MPG?
Any suggestions on who has the best prices on Maggie HFs and which part number?

 

I should mention this occurs on the factory tune too, so not just a tuning issue. Any possibility that the Gotts mod will work on this issue?

 

New development...Truck died about two blocks from the house when my wife was coming back from the store. Started up, no problem, but I can't have her driving a vehicle that isn't dependable. ANY suggestions on what Maggie PN for an F-250? I know it is different than the F-150. Could this have been caused by clogged cats?

 

I doubt that both cats would fail at exactly the same time. Do a google search on TSB 01-9-7. The TSB has a wealth of information on troubleshooting your problem.

 

Thanks for the TSB info! I'll read it much better than I have thus far and see what I come up with. Truck runs fine so I have a hard time believing it can't breathe (exhale) from either nostril.