EGR?

I have 84 cadillac de ville with 4.1 engine the new engine has 60,000 miles and transmition was just rebuild, I had the car parked for a year and before I started to drive it again I changed sparkplugs and sparkplug wires, fuel filer air filer and drained the gas tank but after 2 month of driving the engine started acting up, its starts with no problems but I have to wait for a while for it to warm up before I can put it in drive and if I dont wait it sounds like its about to die and few times it died but started back up also it feels like it has almost no power I tryed T.B.I. Cleaner but it did not help do you think it can be EGR valve because I dont think it was ever changed when engine was replaced and the car had 170,000 before the new engine was put it, I ran computer for any error coded and it didnt show any