95 jimmy vortec - HELP!! plz

help! my boyfriend has a 95 gmc jimmy, i will tell you right off that he is not a "mechanic" at all... one day he got in it and it wouln't start, before i got to see it he had it towed to a "backyard" mechanic of a friend. the guy told him it was fuel pump and charged him $100. to install. he bought the pump from kragen (2 choices $75. and $125. one, you know which one of course- the $75. pump) came with lifetime warranty. the guy installs it and walla, it starts and runs great! for a couple of days. the pump started making a loud noise, at first only when tank was low, then it got louder all the time. so i called kragen back and asked them if they ever have problems with these pumps. they said no that was the first time. (sure) since you have to remove the gas tank to replace, it is not easy job. i asked kragen if we should upgrade to the more expensive pump, but they said the one we bought was good and should not happen again. (but he still has to pay mechanic another $100. to re-replace it) this time when jeff went to kragen to exchange the pump - the salesguy told him that you had to buy this special filter with it (this is same guy who sold him pump in first place) so he brought the new pump and filter to mechanic, apparently the mechanic had found a bunch of old filters on the bottom of the tank. and it is still not clear as to if there was a filter (old) on the first installation.

truck runs great for a couple of weeks, then one day he got in and started it - no power - barely runs - !

takes it to tune-up masters, they won't touch cuz they say it is the injectors?

could all this of happened because of the filter issue?

and how do we fix?

actually me, i usually watch what is done to my car if i don't do it myself

but now im pretty much "retired"

lisa

thank you in advance for any advice