The "volume" check determines the fuel pump(s) ability to deliver adequate fuel based on performance demand. Hard throttle means increased demand on the engine and during this time the engine requires more fuel to develop the smooth performance anticipated by the driver. Low volume from one the fuel pumps can, and often does, contribute to sluggish engine performance during hard throttle situations. I am not certain your vehicle is suffering from a bad or faulty fuel pump but for the length of time it takes to perform this test it is time well spent.

Disconnect the fuel return line after the fuel pressure regulator (bolted to air/fuel mixture housing) and connect a hose to the outlet side. Place the other end of this hose into a glass container (.5 gal or larger), cycle the key several times to determine the volume. If you are savvy with electrical you can remove the fuel pump relay then bridge the fuel pump connections, this is a little tricky on the 107 chassis. If you need some pics to guide you along I might be able to muster a few of them up.