you have 20k miles on yours and they are bare, what where you spraying? And how much.
I have 65k on mine and i have ran 20 or so bottles of 75 shot of nitrous thru it and also had alky injection for 3 years.
I really just think its a crap shoot weather or not your Teflon going to come off or not. Might be something to do with variances on how eaton applied the coating and not what happens in the field.