Scott/James, I thouhgt the least back pressure in a turbo the better. eg none perfect. So the bigger the better but I would suggest 3" to be a waste of money and would go with the
2.5" mandrel also. If 3" normal bent was cheaper it would probably be the way to go.
I have seen many of those articles on the air/fule ratio meters but can't remember what sensors they use to trigger the system. If they use the oxygen sensors from factory cars as I
suspect, then I'm sure I read they don't last when exposed to leaded (super) fuel. What are you going to run in the car.
With a direct path from the turbo to inlet does that mean you are not using any form of cooling of the inlet charge.