unbelieveable

Every time I work on this thing the code changes. I was pulling the MAF code until I cleaned some connectors then it included the O2 sensors and the rev. I couldn't clear the codes either. Today I cleaned the MAF, the thottle sensor, alt. connector, and checked for vac leaks. Now I can clear the codes and as I run it it stays clear. Problem is as soon as I move the car forward a ways the ec light starts flashing constant flashes. I turned it off and checked but no codes. I can reset to clear but it starts flashing when I start moving again. I took the car out and ran it hard after it was warm and it ran perfect. Who knows for how long but it was a nice change. ASny thoughts as to how to keep this light off?
Another question is would a leaking p.s. pump cause vac problems or engine performance questions? Can it be easily fixed?
Thanks, DAVE