Hey all, I've looked everywhere on this site and cant believe no-ones posted on how you know when your turbo needs a rebuild - other than the obvious it blew up!

Mine is leaking oil from the BOV and I'm pretty sure the wastegate has rusted shut cause I get a ch ch ch ch noise at full boost running up a hill. The truck goes really well, plenty of power (I don't tow so 2.8 is ok) so should I rebuild now or wait for it to blow?

Thanks for any advice.