I have the wastegate from my old turbo set up for sale. Its a Tiel 44 mm annodised purple external gate. Still in top condition. No marks or wear. $200 not negotiable
dissasemble it to the two purple anodised parts and use some caustic soda used to remove adodising off alloy bmx parts back in the day
just a tip it doesnt take long so best bet is to keep pulling it out and give it a wipe then back in again for a while then test it again.