Well as far as I know Infinity Ward hasn't banned anyone's MAC Address, they've only been banning accounts and console id's. So there is no need for that mac address change you did. But make sure that your CID is changed, because your console id gets reset every timeyou turn off your console. So start up your console, change your console id then go on ghosts.
could be that you're still using the anti-ban tools which they can detect now and will give you insta ban. So no matter how many new CID you use. if you use the anti-ban tool you'll get it ban.