mlstilos

hi i have a 98 ml320. my truck was idling rough, i cant get more than 4000 rpms and go over 60 mph at times. whenever i stop at a redlight or stop sign my truck kills on me. i changed the air mass sensor and the egr valve. i tried to take off the egr tube to clean it but i cant get it off. any suggestions on cleaning it or removing it. now my truck runs better but when i get above 4000 rpms again it sputters and when i stop it always kills. please help.