Sydneykid - thanks for that info - makes sense - Must have missed the other threads that you covered that in - Thanks again ! I suppose, what I should have mentioned was that 'if it didn't cost me anything' honing/polishing the std plenum.. blah blah... ? No need to reply though now, as you said, this has been covered elsewhere.
Steve - V. Interesting.
OK, I have in my possesion a stock RB25DET plenum and throttle body. I'll get it flow tested using the same people and under the same conditions as my front facing plemum and I will post the results. It will take mabe 2 weeks or so.
I nearly was able to purchase a Greddy plenum (but got out bid and I didn't want to pay anymore) - So if I was able to get it, I would have flow tested it too - just for fun ! :)