If you are not sure why all those channels need to be there, are you sure you want to expose yourself to the risk of making a crap product that makes the car idle like a chaff cutter and run well only on WOT?
Sure there might be a market for that, but the largest market is general street. There are very few actual race only skylines out there. As r33_racer said, there would be a market for an affordable adaptor for 26 plenums, but I'm working on that.........
Then again if it came on the market at the 350-400 price range there would be plenty of suckers buying for bling.
ROFL at Bass and the answer to all things aerodynamic. From experience it tends to be a little more complex than that.