Did you get yours through Redline?
I bought my intake and carbs about twenty years ago from another RX-7 guy I autocrossed against. He swapped up to a 13B peripheral port motor and a 52mm Weber IDA, if I remember right. He took it to the SCCA Nationals and one of the rotor bearings walked out on his first run, ruining the engine. He retired the car after that and focused on the new shop he was opening.
I bolted the intake and carbs onto my half-bridgeported 12A. The inner primary barrels fed the mild street ports (think street/strip cam), but once you got above 3000 rpm you could floor it and the outer secondary barrels fed the race ports (full race cam). Poor man's VTEC.
Edit: My intake is from Rotary Engineering. The were already long gone when I got the manifold.