The cat's on my 06 F250 5.4L burnt out at 17,000 miles (I bought the truck new in Sept of 06) I was getting abt 5-6 mpg at the time and the truck has Zero power. Lucky warranty took care of the problem, but I think it has returned again... truck just doesnt seem to have the power it did, unless its just this horrible "gasoline" we have now I days... yet again its got 92K on the clock.

I run a K&N CAI on my truck and love it, havent had any problems with it at all... just have to clean it more often than the drop-in filter in the stock box. Doesnt hurt to take your MAF out every once in a while and clean it.

Redford: The 05 and up trucks have a different Y-pipe design than the 1st gen super duty's, the y-pipe is much less restrictive. no need to replace it.