What could cause this

Had problems getting the car to run finally got it to idle real well with no problems. Now when I try to give it gas it hesitates. I can get it up to about 4000 rpm`s and it will hesitate between 4k down to 3k rpm`s with idle held in same spot. If I try to give it more gas than 4k rpm`s it tries to die out. Not sure what would cause this as the check engine light does not come on and I have replaced fuel filter. Fuel pump relay, cleaned maf sensor checked tps sensor and replaced 2 cracked vacuume lines to get it to this point. I`m thinking maybee a pluged fuel injector but not sure. Any help will be greatly appreciated