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[patsmx5]

Ok, I have a 99' mazda miata. 1.8L BP DOHC I4. Lots of headwork and whatnot. It breathes well for a BP.

I'm unsure exactly how I'm gonna upgrade my fuel system right now. I currently have RC Engineering low ohm 550's installed in the otherwise stock 99's returnless fuel system. I already have a new Walbro 255HP and a new Mallory 30-100 PSI 1:1 boost reference fuel pressure regulator waiting to go on. Will likely keep the factory rail, factory fuel pulse dampers, factory lines, etc. Just be adding a regulator and return, and bigger pump.

I could keep my 550s and set base pressure to say 80 PSI with the reference line removed, and then it would run 80 + whatever my boost pressure is when in boost.

Or I could keep a lower pressure and get larger injectors. Which would you do and why? I was planning on getting some used 1000cc low ohm injectors from a buddy but he sold them before I could get them. New ones are $$$ and I don't want a shitty injector that doesn't spray well, or has a reputation for failing. Also, is there anything else I should plan on doing to the fuel system? Looking for a solid 350whp when I get the rods in.

[patsmx5]

do you actually gain anything from running 80psi

More fuel, and possibly a better spray pattern.

[92CXyD]

I believe some most stock inj. do not like 80 psi. usually 60 psi. is the max safe limit. ;D

[papercuts]

Didn't know miatas came stock with rc  550's. Learn somthing new everyday.  Der

[stealthiskey]

go with bigger injectors and bring the fuel pressure down a bit lower.  While your injectors will flow more at higher pressures your fuel pump will generally flow less. 

-Overworking the pump is not great. 
-Larger injectors will give you room to expand.
-You could sell the RC 550s and buy larger for almost no extra cost.