Check Engine Light Help

I am a fairly new member and I need some guidance please on my 94 C220. Recently, I had a check engine light and as a result I took it to my local mechanic where he found a vacuum leak near the mass airflow sensor. After repairing the leak, the check engine was off for several days but after a couple days it came back on. I thought the problem was fixed because I had surging and poor fuel performance, which I still have these problems. I am interested in finding out if I need to replace the O2 sensor or mass sensor to correct this problem.

Thanks in advance.

Richard