Lean running F-150 ?

[rando]

Hello ,
I've got a 2006 F-150 , 5.4 L with an Airaid CAI and Magnaflow SIDO exhaust system .
I downloaded the canned tune from my Predator U7151 for the 87 octane Airaid CAI .
It runs great and I am very happy with the performance !
However the polished stainless steel exhaust tips that came with my exhaust system have started to get a yellow discoloration .
I know on my Harleys that when the pipes start to yellow , it's a sign of running too lean .
Could this be what's going on and if so what would be your recommendation to solve the problem ?
The truck has shown no codes for running lean .
Thanks for your help .
Randy

[mikel]

I highly doubt it is running lean, especially if there are no codes...

[rando]

What do you think may be causing the yellowing of the tips ?