This is a copy of an email I sent to a member asking about the GReddy PRofec-B Spec-II and how to set it up. The links aren't my work, just a collection of what I found that works.
First, make sure it's installed right. This is easy to do wrong. Here are a couple of pages:
Greddy Profec Installation and Tuning
GReddy PRofec-B Spec-II
Quoting RRE's instructions:
"Mitsubishi have fuel pressure controlling solenoid valves. Make sure to get the pressure from the line between the intake manifold and the solenoid." This is where most people make a mistake on DSMs. If you have removed this solenoid, tee it in at the FPR line.
You'll basically remove a ton of hoses and such. You need to keep the electrical connector to the factory boost control solenoid. Don't forget to cap everything off that you removed. It's a good time to remove your EGR valve if you are going to. Clean up them hoses. Run a good cat.
Once it's hooked up right, just tune it like the instructions. Piece of cake. Works like a charm.
Here's a good link for the tuning piece. Makes plain English sense of what the knobs do:
How To Tune Your Greddy Profec B spec II