Purpose of holes in housingss (below exhaust) and whether you can swap housings
 

I'd love to get some feedback from experienced engine builders here to offer some advice regarding an engine build. I have an engine from a 1996 JDM FD3S that was rebuilt in Germany, and the front and rear housings are swapped, from my understanding due to matching rotor width to housing width (clearancing)
From my knowledge, the housings should only differ in the stamping on the top side (F or R) but I thought they were mechanically identical.

A couple of guys are currently in the process of installing this engine and had trouble firing it up, they consulted some local RX-7 'experts' to help with this issue. They claim that it's a problem that the housings are swapped, and that it's related to the airflow going from the intake ports to the 2 small holes below the exhaust port.

What they literally told us was the following (drawing below to understand what I mean)

"If we blow inside of the air inlet (marked as yellow) then it comes out of the red hole, but it should be coming out of the green one"

https://cimg0.ibsrv.net/gimg/www.rx7...f8056c4ba8.png

What I would also like to note is that the car is in a fully stock configuration at the moment, but emissions will eventually be removed.

Are they correct in saying that the housings are reversed, or shouldn't it matter? I'd love to get your opinions on this... Many thanks in advance.

Best regards,

Nick

the housings are marked Front and Rear, should be a little F or R, and one is blue and one is pink

the square port under the primary intake ports goes down to the exhaust ports, and the difference in rotor housings is that the passage is only drilled on one side. if you assemble it backwards, it blocks the ACV and air pump off and it will never pass emissions. it is actually possible to drill the hole so the passages still work, and some older Rx7's were that way so the housings were the same front and rear (81-85)

the holes under the exhaust port were for EGR.