350 engine flutters during ecceleration

I have a 1989 sierra 3/4 ton 2 wh drive with 280 thousand kms on it. I bought the truck and drove it back and forth 1 hr each way for a month straight.
It ran great, other than the oil preasure gauge reads max most of the time 400kps. The guy I bought it from said that the bottom end was going. What ever that means? Well one day I really came onto it at a set of lights and shortly after that when id slow down, Id have to take it out of gear and keep the revs up or it would die. Idle down to nothing. The next day it was fine. It was fine for about 2 weeks, then started idleing rough and fluttering as it picked up speed. This lasted till I shut the motor off and restarted or ussually by the next day it would run fine again. Well its back. This time it wont go away. It runs great when I first start it and let it warm up and idle down. But engine flutters when I gradualy step on the gas to gain speed. If I let it idle to long, the service engine light comes on. One time it was idleing I heard the rpms quickly shoot up for a few seconds then back down by itself. It got a new egr and distributor and button. What should I be looking at next? Converter? THIS SITE IS AWESOME GUYS !