Jeff, I didn't realise I was that close to the edge on it, but you've caused me to look into it which I thank you for! I'm used to this pump on larger engines running lower boost but making more power, and looking again for a higher boost 2 litre is important...

Assuming I'm droppping from 13.5 to 12.0V across the pump under load on the stock wiring, on the Walbro at 90% IDC on 560*4*1.095 I need about 132 lph, so I won't be returning much of the 140 lph the pump should manage at that pressure and voltage. Hopefully it will be a bit nearer to 185 lph at 13.5V, but doesn't give me confidence to increase the pressure any more.

 

Jeff Lucius has some nice graphs on his site that will help you figure out how close to the edge you are running. I run a Supra pump myself, and the Walbro HP is about the same. The regular Walbro 255 takes a pretty big dive >70 psi.
http://www.stealth316.com/2-fuelpumpguide.htm
Jeff O.
aka keydiver

 

I installed my Walbro and logged my AFR's. They did not change.