vauxhall zafira spaner light ?

i have a vauxhall zafira 2004 with service spanner light showing on dash when this is on can not rev above 3000 revs i have had vauxhall do a donostics on it and found a cam position sensor faultly now replaced and no faults showing on donostic test but still problem remains been told ecu could need replacing but some days i get in car and spanner light not on and car drives fine till engine warms up then goes in to what people say is limp mode ie wont rev above 3000 revs so madding can anyone help please