My fuel pump was supposed to be replaced with a walbro 255 but im not sure.. seems as though it maybe having a hard time keep psi

 

Walbro pumps typically make more noise than stock pumps, getting them the nickname "whinebro". But a failing pump can also make noise.

Check the actual pressure and see if it's dropping.
Check the voltage going to the pump.
Are your fuel filters fresh?

Not much you can do to identify the pump except pulling the pump out of the tank to inspect it. It's accessible though the trunk rather than having to drop the entire tank, so it's not too bad. If it looks like a walbro, then you need to check if it is actually a genuine walbro or a cheap knock-off.

 

Walbro 255: Walbro 255 Fuel Pump Kit 86 88 Mazda RX7 | eBay

They're smaller than stock pumps and are silver in color. As mentioned, you have to pull the fuel pump assembly to check. It can be done in about 10 minutes if the screws holding it onto the fuel tank are not seized.

 

You should be able to hear it for sure