The wear in the original guide is usually not a problem as long as the boring tool will straighten the guide ID. Unless the guide is really shot (over .015 wear). Then replacement with solid guides is done.
Iron guides are used only because they are INEXPENSIVE!! Check most aftermkt heads you will not see iron guides in anything above base line..
If you are getting "Gold" you have an abrading problem. This is an installer problem not the product.