I have only ever owned 1 4-stroke that stayed with it's original exhaust. They were either rotted out when I got the bike, rotted out shortly after I got the bike, or had rotted long before I got near it.
I get why people want to fit original pipes on early 4 pipe machines, as they look so 'right' but then exhaust design got a lot less pretty, and there were pipes like the Harris 4-1's that looked so much better.
Sadly for me, I know exactly what exhaust I would like on my F2, but nobody makes one like that......
Delkevic looks quite nice, but the headers pipes take an odd angle under the motor that I don't like