hi
I have 1000 cc bosch ev14 injectors (at 58psi)

At either 45 psi or 58 psi, the injectors are more than enough for my setup.

What base pressure do you recommend me to use them on my ls/vtec and why ?

Thanks..

I would use OEM pressure specs for a gsr. which i believe is 43psi, so 45 is fine...i believe 50-55 psi at WOT. but at idle stick with 43-45psi. There is no need to turn up fuel pressure to get more fuel. Since you said yourself the injectors are more then enough for youre set-up so more fuel should be given thru the Tune, not thru higher fuel pressure. usually higher pressure is used when you are running out of injector and need to increase the amount of fuel given without going past the maximum recommended duty cycle on the injector

High pressure for better atomization.

does "better atomization" ALSO mean better fuel economy when daily driving ? or it has nothing to do with it ?

Correct, but to a certain point on some injector designs/sizes. But that's a big injector, so unless he shortens pusle-width, then it will run richer. So if you up the fuel pressure I would get a new tune for it.