vauxhall astra mk3

[aabbccdd]

when driving along if i lift off the gas for a few seconds the engine light comes on and will not turn off untill i turn off egnition and put it back on again no real diference in preformance when light is on just a bit spluttery at idle speed i have chainged inlet manifold gasket , idel control motor and throttel positon sensor but makes no diference could eanyone tell me whats wrong thanks