305 / 350 TBI injectors, fuel pressure, cleaning etc

Hi

Im a recently proud owner of a 1989 G20 which according to rpo codes should have a 350 in it, but it turned out to be a 305 from 1986.:innocent2: The problem is that the injectors are 350 but i managed to get a hold of a full 305 TBI assembly so my plan is to change them.

Now som things i wonder
Is far as i understand the 350s run 16 psi and the 305 run 12? The thing i don't understand though is that in the 350 TBI the pre tension on the fuel pressure regulator is pre-set harder than on the 305.. should it not be the other way around? Or is fuel pump different on 305/350?

As i plan to change injectors i'm wondering about the metal rings. 350 came with o-ring on bottom, and on top a sort of o-ring with a groove containing a brass ring.
305 came with o-ring bottom and then on top a o-ring with stainless ring under it.
Someone said to me that the purpouse of the metal ring is to provide ground, but wouldn't ground be from ecu wires?

I plan to clean injectors as i have access to ultrasonic cleaner and electronic equipment so i can activate it by pulse. What cleaning agent is recomended to use? Also what amperage does an injector pull so i dont fry them? Looked at schematics and they seem to run straight of ecm?

I wont be able to professionally test them after cleaning. But what difference does this make on a vehicle not aimed for perfomance, but just good milage and smooth engine without to much fuel trim. Does flow matching make a good perfomance increse? Or should it bee enough if i can get my orignal GM ones clean? I dont really trust ebay ads saying they sell injectors flow tested and matched..

/Alex