In the process of tuning my FAST sequential system now on my Fury (Classic FAST, not XFI). I farmed out the intake conversion but did all the other work myself in my garage. It's very doable, but you need to devote some serious time to it. I have not had much chance to drive/tune the car (4 month old baby), but it's going to take some time to get it so I can do more than go around the block. Depending on where you live, you can pay to have tuning done of course.
I bought my stuff used or very good deal new over several years and pulled some favors on the fab work.
IMO it's much easier to get a carb working correctly, but I'm working towards other long range goals with mine.