The data in this guide is from an article done by Turbo & High Tech Performance magazine. I will compare the Walbro 255 & Bosch 044 fuel pumps using their current requirements & horsepower capacity vs boost pressure.
Up to 30PSI boost and up to 600bhp, the Walbro 255 fuel pump is probably the choice
Which Fuel Pump Do You Need?
Ultimately this depends on the boost pressure you will run to meet your horsepower targets
Why Not Just Choose the Bosch 044 Fuel Pump?
It will need new plumbing and depending on the boost you are running, also new wiring.
If your power and boost targets can be met with the Walbro 255 (GSS342/340/341) it makes sense to use the Walbro because you can use the car’s original wiring and more often that not it will be a direct replacement for the factory fuel pump.
Basically the Walbro is much easier to install.
The Graph & Data
If your boost target is 30 PSI or less and your power target is less than 600 bhp it looks like the Walbro will do the job. More than that and we are getting towards the limit of the pump and this is the point it may be a good idea to choose the Bosch 044.
Another reason to go for the Bosch 044 over the Walbro 255 fuel pump is if you are looking at running boost pressures over 40 PSI. The power handling capability of the Walbro drops of significantly above this pressure.
The Bosch 044 fuel pump can support around 700 bhp at 55 PSI of boost and around 750bhp at 35 PSI of boost but I would recommend upgrading the fuel pump wiring to deal with the current it needs.
Note: There are other fuel pumps available on the market