1.1849 vs 1.2260 rho temperature gradient (24 celsius vs 15) equates to a 3 percent boost based of air density alone in a perfect world where a car is well tuned.

To test for backpressure restriction, I don't think an R34 with a NEO6 is going to push the flow restriction limits of an open pod filter. You'd need something a lot beefier.

Naw, that's an RB25DET with a NEO head and a small T25 flange turbo, not an RB26. It won't flow really hard. I still own one of these bastids haha!

Plus my experience from the RB25DET is that without a tunable ECU like an Apexi PowerFC and a decent turbo, it's pretty hard to max out airflow as the stock ceramic turbo is shit.