No he said the same pressure through both. If you run 105psi on stock injectors and it is tuned pretty good then you run the same pressure w/ the 30#'s then you'd have WAY too much fuel which equals LESS power. If more fuel made more power w/ the 315's then he'd have to have been rediculously lean w/ the stockers at the same pressure.

*edit* ok you edited while I was posting and added the "more air" part ;) But w/ everything the same but injectors then you have the same amount of air. So putting in the bigger injectors at the same psi would hurt power.