Looking at a nice 11 limited F150 w/145 k. Asking 20K ish for it.. Anyway.. I read these engines have valve spring issues. Is it just a 1 in a million internet thing? Sometimes it is a quick repair ( i had the issue on the Lincoln DOHC) but it is usually the reason why the engine is trashed, they are bulletproof otherwise. Worth swapping them out for PM? I also read it happens even in the later models, sometimes in warranty, so what you buy could be the same issue. Wonder if there is a way to find out how many of them ford sells.