Some time ago I purchased a flashable SBEC and one question that arose during my research was what is the difference between the TI and the TII boost control methods. I figured it out however in the Turbonator SBEC thread somebody posed the same question. I figured I'd share what I had learned.



The above illustration shows the Garrett style TII boost control method. In this setup boost from the manifold vacuum/pressure source is plumbed either to vent or to the wastegate. The computer controlled solenoid directs this operation.



The above illustration shows the Mitsubishi style TI boost control method. In this setup a Positive Actuation Restrictor harness, shown on the right, is used. There is only one vacuum line from the PAR harness to the wastegate solenoid. The computer in this case only vents pressure to regulate boost.

I learned a lot from this post.