1) In the WB literature, the WB Greenstar Hightflow has a max ouput of 29.2 Kw, and a max flowrate of 20 l/min with a increase in temp of 35 deg C. The 40 HE Plus can output 40Kw and only manage 16 l/min but has an almost identical efficiency.
Q - How is this possible?

2) Are manufacturers boiler statistics accurate?

3) Does WB performance degrade after 1 month / 1 year?

4) I have read that it is illegal to place a pump in an unvented system. Is this true? I wondering if a flow limited pump exists (and it legal) that I can put after my mains feed for cold water into kitchen.
This would be able to boost the pressure through the maze of pipes in my house and ensure that the showers can operate at the maximum flow available. (Shower has 6body jets at uses about 18 l/min )

5) Is there such a thing as an unvented Cold Water tank with an expansion vessle inside? I was thinking that this would enable a short term higher feed rate of the hot and cold water requirements of the house.

6) Are there any recent high flow combi boilers equivalent to the WB Greenstar 440 that are Better that it terms of Continuous unlimited Flowrate. (Note: I am not looking for a multi boiler info, nor info on one that involves storing hot water when not in use, just continuous HW supply)

Cheers,
Antony