A little Turbo Selection Help

I doubt the turbo has a positive seal for when you have vacuum (which will pull oil out of the cartridge even with oem diesel turbos that have a ring seal). 5-6psi is reasonable with a draw through carb. Searched for some general online info about it: Rebuild IHI RHB5 and add Carbon Seal – Dr. Scott M. Baker

All sorts of other details to consider such as carb icing when colder than 50f outside. Run as big an oil return as possible straight down out of the cartridge because it will be foamed. If it backs up, it will dump into the engine similar to having vacuum.