I've been researching intercooler sizing, and I think I have a viable plan but I'm hoping to bounce it off of some of you more experienced turbo guys.

My planned setup:

-EJ25 (2005 STI motor)
-Garrett GTX3071R turbo with external wastegate
-Target HP = 280-320
-818R intended for track-only use.

The turbo is large for my power goals, but my engine builder recommended it as an option and the LB/MIN flow rates I've calculated would put me exactly in the middle of its optimal efficiency range, which should mean a cooler intake charge at sustained WOT on the track and lower turbo RPM for less stress on the turbo and oil system, among other benefits.

I want to use the side vents/scoops for the intercooler(s). Since the side vent openings are very small (I plan to enlarge them like Hobby Racer did), I'm considering splitting the airflow from the turbo outlet to two identical intercoolers, one per side vent. If my calculations are correct (and that's a BIG IF), my turbo's CFM output will be very comparable to the stock turbo's max output - mid-400's CFM, 460 to be exact. That makes sense because the stock engine/turbo produces about 300 hp, and I've seen someone report from an unknown source that the stock turbo produces 435 cfm. Therefore, I'm thinking the total volume/flow capacity of my dual-intercooler setup should be roughly the same as the OEM TMIC.

So here's a comparison between the OEM IC and some custom-size cores I found from Bell Intercoolers:

The OEM STI intercooler's core measures 18.5 x 6.625 x 3" for a total volume of 368ci. I have found no flow data on it.

The Bell A300051120 (https://bellintercoolers.com/i-30005...ficiency.html#!) measures 12 x 5.1 x 3" for a volume of 183.6ci. Multiply that by 2 since I'm using 2 of them for a total volume of 367.2ci. Bell claims it flows 261 CFM (again, 2x = 522 CFM total).

My volume calculations do not account for internal construction differences between the OEM and Bell IC's that might mean more or less air capacity in the IC core, but hopefully that is minimal.

Will this work? Am I out to lunch on this idea?

Any suggestions on Intake pipe sizing?