the intercooler piping looks pretty small in diameter, like around 2" or 2.25" for most of it. hard to tell really. but even with all that piping, you're not going to see much of a noticeable difference in lag and throttle response because the stock turbo is well, small and responsive. heck, in stock form, it's already a 1/4 blip of the throttle away from full boost it seems.
it looks like a quality kit esp with the shiny piping and i love the way they integrated the intake filter in there. genius! i do think the BOV location could have remained a tad closer to stock, you would almost think with a setup like that, that you could just put the MAFs housing in the hot pipe and have the BOV nearer the turbo outlet and just run blow-through MAFs. there is plenty of straight pipe on that hotpipe to allow for it too without causing turbulent MAFs readings.
the biggest thing with the TMIC is the heat soak, which is only gonna be a big deal if you're doing something slower like autocrossing, but it seems I've seen alot of speed 3's doing auto-x and havn't heard any complaints about heat soak...but i'd like to see some tests maybe on temps. plus it would depend upon the courses, some of the miata courses down here are super tight and stay in very low speeds, not allowing alot of airflow to the TMIC, where other courses are more open and have some straights or faster areas to get some flow going.
in the end, i love the kit, but i'm going to stick with my TMIC (or an upgrade in the future). i've never used meth before, but that could be an option as well.
plus i love the sleeper status with the stock speed 3 setup - no FMIC, no SMIC in the side of the bumper, no suby-style hood scoop.