need help please
 

alright guys. i have a 98 amigo 2.2 2wd and while cruising at any speed it keeps pulsating really bad and wont go over 55 miles per hour. can anybody help me out on why this is happening. it has never done this before. a few people said egr valve could be stuck open but i don't know whats going on. this is my first Isuzu. any help would be great. thanks in advance everybody. i cleaned my egr valve and replaced my throttle position sensor. it runs fine while cold but once it warms up its pulsating again while accelerating. if anybody can help me out that would be great,. this is my first isuzu and i'm lost on what to look at for this issue.