I have a 1990 dodge dakota 4x4. wont run over 2000rpm.?

1990 dodge dakota 5 speed, 3.9 non magnum. 4x4. ran great until cold weather. now runs fine until warm, then starts to gradually die out after 2000rpm. I got it good and hot, and hopped out & poped the hood, after the intake cover was off, i went wide open throttle & the injectors started to not spray fuel. problem is worse when under load. Help.? already replace temp sensor, possible TPS? fuel pump or filter? as my whits end & winters here.