I have a ST205 Celica, no power mods other than basic intake and exhaust work, will buying a walbro 255lph pump cause me to run rich?
or will I see any improvements in any rpm range?

The st205 always run way too rich, so no benefits from putting in a walbro until you start serious modding.

When I upgrade my fuel system I'm going to use the factory pump to feed a surge tank and an external from there to feed the rail

would there be any difference as the stock FPR will still keep the same pressure in rail?

Intank pump upgrade wont do anything different unless your factory one is worn out or broken. I don't know how many LPH the ST205 factory pump is but it's obviously fit to feed the factory 540cc injectors at standard pressures. Only reason to upgrade intank is if you plan to upgrade your injectors or your factory pump is worn out and want a cool buzzing noise every time the cars running.

Surge tank + external however will give you benefits of preventing fuel starvation during hard cornering and give you a base to upgrade your injectors should you choose to do so in the future.

>


Not really building for circuit racing, more of a 1/4 mile car I'm building, so the surge tank won't be of much use here, So then theoretically it should be safe to boost around 14-15psi on the stock CT20b turbo? with no fuel upgrades? I am planning to get a AEM wideband sensor with guage so I can monitor what my fuel is doing, just trying to avoid ever leaning out at all costs.

probably FPR is your answer, im currently looking into installing one myself, since my rev3 3sgte has higher compression (head, pistons) and plugs show some lean fueling

due to the nature of the head and manifold design means #2 and esp #3 cylinders run leaner than 1&4.

but in general theres a blanket rich condition over the entire rev range and load range up to 17psi+