Flow capability amount of pressure it can hold really about it nothing else. You need better rails when running bigger injectors and bigger injectors mean more fuel more pressure so more volume. Thats when doing some research would come in handy on finding what rails flow more volume and capabilities wise
1996 Mustang GT, 17x9 front and 17x10.5 cobra r replica rims, 255/40/17 front 285/40/17 rear at the moment,
o/r x-pipe flow master 40 series dump downs, cai/ram intake, 75mm c&l throttle body and plenum, pi heads and intake swap, msd wires, stock gears, untuned at the moment, no dyno numbers for now.