[ http://www.z1motorsports.com/product_info.php?cPath=6_17&products_id=4293 ]
To me this does not read like modified 270cc injectors.
"JECS, the original equipment manufacturer trusted by Nissan to supply the stock fuel injectors for the Z32, now offers high performance upgraded fuel injectors in several larger sizes. These injectors are 100% brand new and are backed by a 3 year manufacturer's warranty. "
Don't you think Nissan does the same....meaning they are not in the business of manufacturing injectors. They take JECS and modify and flow test to 750cc?