There is a weird rattling noise when I start my car the noise is coming from under the car around the back of the front wheel I was thinking it is the cat but I don't know is anyone else noticing this. It only last like a second or two.

 

Most likely it's just your motor. The top end of all the 3.5s make that sound on start up, until the oil is pumped up there.

 

This supposes to be the chain tensioner. Be sure to keep your oil level at high mark. The only way i found around it is parking my car nose up and right (passenger) side down.

 

http://maxima.theowensfamily.com/tsb/NTB03-060.pdf

 

Is that a recall.

 

no TSB = Technical Service Bulletin

Nissan has deemed it to be a non-issue similar to the oil burning issues

You aren't really doing any damage unless the sound starts sticking around for longer than a few seconds. Most people have seen improvements using synthetic oils and keeping it topped off.