I wasn't infering you had copied the Jenvey pleunum... Great minds do think alike though.
But it is similar.
http://www.jenvey.co.uk/home/throttle-body-kits/jenvey-dynamics/mitsubishi-turbo-70mm-throttle-body-kit-ckmm01
http://www.jenvey.co.uk/home/turbo-plenum/jenvey-dynamics/turbo-plenum-sm-60mm-inlet-apsc-60
Jenvey are one of the world leaders in aftermerket intake design. I have seen a one off Jenvey intake (in the US) for an rb26 that was amazing... very very xxx'y.
If I was going to fab from scratch an intake, I personally would look at the Jenvey designs and start there....
Either way whoever designed your's, has a good handle on intake design.
Cheers
Justin