G40 pump is 75 l/h at 3 bar.
75 l/h is 1250cc/min, i.e. roughly equivalent to four 310cc injectors at 100% duty cycle. I've yet to map any G40 that needs to run 310cc/min injectors static, though Yoof's isn't miles off.
Obviously it's not quite as simple as that, as you want some headroom to cope with transients, and also you need to know what the pump does above 3 bar pressure given that it's for a boosted motor. A 200bhp G40 needs approx 1000cc/min = 60 l/h, which leaves you a bit of headroom for those transients.
I've tested my own motor with a 130 l/h Bosch pump and the stock 75 l/h one, and I'm running just over 200bhp. The fuelling shows no differences, even on high boost transients, between the two pumps. However, unplug the inline pump and run just off the lift pump and it starts to go lean on transients and even leaner at high rpm/high boost. Though not lean enough to make it run like a total sack of shit, which is probably why people don't notice they've got a dead/dying inline pump - especially if it decays gradually.
There are loads of pumps available that do more flow at 3 bar, but I've yet to find one that uses the same electrical connectors, so it means a bit of cutting and crimping. I've been trying to find the correct mating-half connectors for the G40 pump, that way I could make people automotive grade link harnesses to hook up an 'uprated' pump to their existing wiring. If/when I find one I'll let people know!