have a look at the new Aeromotive pump!! direct replacement and a single should be good for 800 hp

The car is gonna put that to the tire, so I really dont have a choice.

I've been running twin 255 for a while no problems

There are lots of China made Walbro 255 knock offs out there. Be sure you have real USA made pumps....Racetronix has them......wouldn't trust any from Fleabay!

Since your fuel pressure fell make sure your filters are the proper ones and that you don't have a carb style somehow accidentally sent out. Also make sure they aren't knockoffs. Not sure how you tell. Dedicated quality (Bosch) relays or similar only.

Are you on pump gas or e85?

I'm going to run 2 of the Walbro 400/450lph e85 pumps for mine. Should support 1000rwhp+ on e85 with -8AN feed line.

so the af was 12:1 ? what was it normally or what should it be at WOT ?

12:1 should be fine for NA , but i guess boost is a little different ?

The OP hasn't been on in 2 years, I wouldn't get my hopes up about getting answers.

I dont know is it same in US but there (Europe) Bosch gives only 500 hours warranty to they pump when using E-85.

Water and E-85 is really bad to non anodised aluminium.