Have you looked at the 1g in a 2g article? there was a thing about installing a potentiometer (sp?) on a certain pin. In this case the ECU was looking for a certain Barometric pressure from the sensor and it would never get it. So by installing the potentiometer you could basically set it where you wanted.
My car had similar issues, would start fine, maybe idle good for a second, but then after a minute, would run real rough. Installed the P meter and you can adjust it till the car runs smoothly.
http://magnusmotorsports.com/wp-cont...02/1gina2g.pdf
Look at pg 10 for trouble shooting.