1994 Chevy Beretta EGR

I have a 1994 beretta that I bought back in june and it had basicly sat for a year not drivin. It was really ruff driving when I got it and thought it was because it sat for so long. When I didnt go away I looked into repairs. It used to die while driving, shacks all the time, has no horsepower, and vary vary poor gas mileage. I replaced the O2 sensor and that fixed the dying part of the problems. I had the car checked out and was told to replace the EGR valve so I did and it drove great. For 3 days and now it is still shaking really badly and still has no power and still gets bad gas millage. I noticed it does not have a Catalytic Converter as well and im wondering if that is the reason for all this too. The EGR valve seems to be all gunked up when I take it off to clean it every time and this last time I cleaned as much as I could of the valve, hose, and whatever else it was connected to that I could get to with a toothbrush untill I was getting nothing but clear cleaner back and not build up. My question is, is there something else I should be looking into to fix this car or something else I should be cleaning to get this buildup gone? I thought maybe the vacuum line was clogged or dirty but dont know how to clean that either.