I would try putting some silicon grease on the rubber plugs. You can get it any auto parts store.
As for the Westin Bull Guard, I would make sure you have the correct part number, first. If it is, or you have more problems, Westin has a technical support hotline:
800.793.7846 Mon-Fri between the hours of 8:00AM and 5:00PM CST
Their website is:
Westin Automotive
Squeeks can be a tough issue to deal with even when you do have access to the vehicle, let alone on an online forum. Are you within your warranty for squeeks and rattles or was a complaint made to the dealer about it in the warranty timeframe? If so, I would suggest taking it back to the dealer or contacting Nissan's customer service hotline for assistance. Unless they've changed it, it should be:
1-800-NISSAN-1
Remember, the best way to be able to have your noise diagnosed and corrected is to demonstrate the noise to the service manager or (better) the technician that will be working on the vehicle. The best way to do that is to go on a road test and let them know what noise you are complaining about.