I took my 9 turbo apart to clean and service. Everything looks good.

I'm going to put it back together, but can't figure out if I should replace the compressor o-ring. It's not torn or ripped anywhere. A previous evo 8 turbo that I took apart had oil around the O-ring. But the 9 is dry. Anybody have some information on that?

Plus if anyone knows a vendor that I can buy the o-ring from if needed, it would be greatly appreciated.