Would it cause issues if said unstamped champion plugs were used in the turbo engine? I have a 4yr old astra 1.4 turbo and all plugs look terrible, they are champion, apparently was serviced prior sale. Only drove it for 10,000miles. The ceramics of one of the plugs broke and fked up my engine...the astra j 1.4 and 1.6 use champion GM stamped plugs
and the 1.4 turbo and 1.6 turbo use NGK GM stamped plugs
Happy on any advise about this topic.