ok if you look at the tomei adapter kit. The metal reducer is the same thing I am talking about. Just get a reducer silicone coupler like the metal tomei one.
So basically this is how it goes. From the turbo comes the rubber oem intake pipe >> a short 3 or 4 inch long with a 2.5 diameter pipe >> 2.5 to 3 inch reducer coupler >> 300zx MAF. For the 2.5 inch piping, you can use mild steel from any hardware store.
And then you will need worm type clamps. I guess you need two 3 inch clamps and then three 2.5 inch clamps. You can get all that at home depot.
So in the end, instead of spending 80 dollars for one coupler and a piece of metal...you can spend maybe 30 dollars for the same effect.
Here is where you can get the couplers. I really like xs eng couplers.
http://www.xs-engineering.com/...y=203
http://phase2motorsports.store....html
Ideally, a custom mandrel bent intake would be best because the stock rubber intake has so many restrictions. Even with little skill it just takes some mocking up and cutting. I dont know how to weld so I just took mine to a shop.