max bhp from standard injectors?

if i uprate the fuel pump and use a 3.8 fuel pressure regulator would i be able to hit 340bhp with the supporting mods i have?
(but using the standard injectors)

I would say you may be getting up to the limit the stock injectors can handle.
An upgrade to 440 cc may be wise.

Use Bosch 470cc injectors "Astra VXR" injectors. They work so much better than the green 440cc injectors.

Bosch Part No. 0 280 156 280

What is the spray pattern on the VXR injectors?

hmm interesting may have to look into sourcing some 2nd hand injectors if possible. ( from 2 vehicles!)

2 cones, 20° spread, according to one source.

Any idea of the gap between the cones?