...was bad and running lean i? replaced the o2 sensor and no more code but its still running lean i have a gm tech 1 computer its telling me im running lean when i hit the gas it runs Rich then back to lean there are no vacuum leaks at all and it idles at 1175 when you first start but as soon as it warms up and goes to closed loop it idles down to 780 to 900 it goes back and forth on the tech 1 please help.thanks