Gordon, yes and no......both injectors are mechanically the same, flow wise. The necessary pulse with for each injector is halved when the conditions for secondary operation are met. In that circumstance each of the 16 injectors are actually only provided with 1/2 the pulse width needed to release the necessary amount of fuel vs load vs throttle position. The recalibration of the fuel map to delete the secondary control mechanical parts takes advantage of the fact that at some very low TPS % you can have all the injectors firing accurately and not loose enough ( I'm told by people that have this mod ) low end to notice. Now I will allow that most of the people that have this mod also have other major top end work.
At a seminar this year at our Gathering, Dave, Graham, & Jim Ingles spoke about the two injector set up and some of the reasoning. A lot of the reasoning was for stupid EPA and Federal noise standards and CAFE numbers. They knew that they could absolutely meet all those stupid rules if they did the primary./secondary thing with a power switch. They could argue, successfully that all the testing should be done in the "Normal" power mode vs the "Full" power mode as the car is intended to be driven in "Normal" until the situation demands extra power......I know there were proly some raised eyebrows at the EPA but Dave & Company got it past them. Dave & Co also said that they were knew that they could meet CAFE & Emissions without the secondary system being a commanded system, but they were not sure about the drive-by noise level test mostly.
Tom