FUEL PUMPS

i have a old one that im gonna hook up and have my buddy sit in the car and hold it.
now,if theres a LOOSE connection but STILL works, will it still pump at 110gph??....IF it needs 20amps and its only getting 10-15amps will THAT affect it??

im STILL leaning out on HIGH rpms and its GOT to be 1 of 2 things...pumps not getting enough amps to work properly or my pump is bad,which i doubt.