1986 Toyota Van

Electrical problem
1986 Toyota Van 4 cyl Two Wheel Drive Automatic 275K miles

I have 86 toyota cargo van which has approx 275,000
miles. About a month ago I noticed the car surges and idles erratically especially when in stop light. Prior to the symptom, 4 months ago, we replaced spark plug and wire, distributor cap and rotor. After the symptoms, we replaced the spark plug wire again which did not cure the symptom. We replaced the throttle valve with tps sensor (used one from ecology) but without changes in the car performance. I have been reading
so many suggestions and that it leads me to MAF sensor. Am I on the right track? Any help you can extend is greatly appreciated. I love reading all your recommendations. They are very very informative.
April 10, 2010.

Clean out the idle air control valve and EGR valve and test the airflow meter

Apr 11, 2010.