Hey, I'm just busting balls as I don't see many people using XFI boost control except for advanced tuners. After doing some reading up on it I would hook up CO2 or an air pump and run it in open loop to get started.
From what I read you would first run off wastegate spring only to see what boost you have and then set your regulator to 2x the boost you want to add to the boost you were getting from wastegate spring only. So if you get 10psi on wastegate only and want to run 25psi total, you need to add 15psi to your wastegate to get 25psi. So set your CO2 regulator to 30psi (15psi x 2) . This will become your 100% duty cycle point and you won't be able to over boost past this. Then you just set your boost table duty cycle % vs TPS %. You could probably start with a line 0% DC at 10% TPS and 100% DC at 90% TPS and go from there. Not like these curves are all over the place so its just a guess.
The other option would be min MAP setting. Putting a number other than 0 means it will switch to 100% DC until it hits the entered MAP setting. Great for spoolup because you want max pressure on the wastegate while spooling. Trial and error as to where you'd want to set it but I'd guess somewhere a little lower than the desired boost, but if it slows down the ramp too much I'd set it higher.
The big drawback for this simple mode is that it kicks in once you go off idle TPS or RPM. You'd go through a lot of CO2 on the street if you keep the CO2 on whereas other boost controllers usually wait to activate at 2 or 3 psi boost. I'd recommend an air pump in the trunk for street duty so you'd have an endless supply of air. Another drawback is that there is no simple launch mode, you'd have to go into Power Adder settings...
Which means to make full use of all the functions, timed stages, launch mode, etc you'd have to go into Power Adder features which is another level of functions and you have to make sure you aren't correcting the A/F tables inadvertently and have all the correct boxes checked, etc. So you'll be knowing your way around XFI at this point and be heavily involved. The good thing with using XFI boost control would be that you'd have all your info in one single log and you'd know what everything was set at for future reference. Oh, and closed loop has even more settings for controlling the boost to the top of the wastegate instead of just working with open loop duty cycle. I've read open loop has the fastest response though.
I think this is why most people use a standalone boost controller.... The interface is pretty simple and easy to adjust for launch and after launch boost (and stages if you need them). Add a clutch flag to your XFI logs and you have a starting point for your boost controller timing. And you don't need to know much about XFI to get it working.