I was looking at using a 38mm wastegate for my diy project. My car is an 04 with the 10:1 compressions I would be running max 9psi with a mitsu 16g turbo.

A member of my local miata club is selling a used tial 40mm unit, could I use this for my application or is it better suited for a much higher hp/flow applications?

IM thinking if the wastegate is over sized you wouldnt get good control on the boost.

 

2mm wont matter, it would be fine.

 

If it's cheap I'd jump all over it. If its not, just get a 38mm. There won't be any problem with using it though.
-Michael-