I like the premis, but remote mount turbos have a tendancy to burn oil since it can become stagnant in the return line if they arent set up properly. I've been looking at these systems for quite a few years, but have just never really been sold on the concept.
I believe you want high emthalpy gasses to spool a turbo, something this will not typically give you. Granted, its not like most people are going for broke on a stock 3.7, so hell, maybe its worth a shot. It will still be a solid horsepower bump. I really wouldnt worry about lag too much, the air just displaces the charge in front of it, so its more of a steady wave of air instead of a flow.... i really have no idea though, not much information on these kits other than what STS provides.
I know a lot of LS1 guys who have had good luck with them and they seem to make good power. I actually checked out the STS website and they don't list a kit for the V6 cars and I would be a bit skeptical from ordering from that website with this in the descripton
"Being the premier source for Remote-Mount Turbo Systems, STS has a number of upgrade options for Mustang owners who have plans of modifying their 4.6L motors. Please contact our sales team for pricing and upgrade options."