i think the AMS Fuel Surge Tank System will be good enough to support more than 600+awhp.
i will be running a 255lb intake along with AMS surge tank on my setup 2.0l and full race 40r.

If I'm not mistaken, in the Buschur double pumper setup, the second pump is activated via an adjustable Hobbes switch. This way you can set at what predetermined boost level you want the second pump to kick in.

The advantage of this setup is that at lower boost levels where you only need the volume that one Walbro can provide, you are not overtaxing your return line or fuel pressure regulator and fattening your AFR's with the additional volume of a second pump.

EDIT: As to the backflow issue, I think that the pumps are merged with a "Y" junction which joins flow after the pump outlets. The reversion factor is probably not an issue, due to built in check valves. The only real draw back to a Hobbes activated system is the dependability of the Hobbes switch itself.

FWIW, I personally think that it is a neat setup. On my Buick Turbo Regal, I had an intank A.T.R. double pumper setup which consisted of dual WALBRO 340's on a billet "Y" block, with the 2nd pump activated via an adjustable Hobbes switch. In that application my 2nd pump was set to come on above 15#.

Not sure if we covered this but for like up to a GT35R set-up.

Is it possible to just use an inline booster fuel pump, like:

Zex inline booster fuel pump
or
MSD inline booster fuel pump

Maybe a cheap reliable alternative to a twin pump or surge tank setup and good for up to 600WHP?

.

the twin pump setup is cheap