Cars stalls

Hi, I have s 1999 Toyota Camry
LE. About three months ago my
car stalled when backing out of
driveway. Would sometimes stall
at lights and stop signs. Would
always crank right up. As time
went on the stalling got worse as I
drove down the highway but
always start backup. Got so bad I
couldn't drive it without constant
stalling. My son-in-law took old
gas filter out. The gas poured out
of each end really clear and no
dirty gas so he figured the fuel
pump was alright. He put in a new
filter but car still stalled bad. I put
a bottle of Lucas Injector cleaner
and the car drove fine for a full
day but starting stalling again. Not
near as bad before.  Could you
please tell me what could be
wrong. I'm thinking maybe a fuel
pump relay going bad. I'm not a
mechanic and don't have much
help. Thank you