I've burned my plastic cover on the headers a few times. Acetone with melt the plastic off without in any way hurting the chrome. You have to keep going over it keeping it wet (non plastic rag) with the acetone and it will get smaller and smaller. You can try rubbing the stuck on stuff with the acetone. It will melt it away.
This totally assures you will do nothing to scratch the chrome or hurt the finish.
