2003 Boxster rear end noise

[eomak]

Hi,new to forum at just picked up a 2003 50km's boxster 4 full year warrnty.I also own a 1980 911SC and still runs great.I think this topic been coverd before and hopeing its the same thing as others.When i was looking to buy this car i went over it few times driving it,listening to engine driving it again and sounded quite,smooth clean running.I was going to take it to my porsche mech. to have it inpected but decided not to because the car's in mint shape 1 owner and sounded great and thought i guess worse thing would be is a new clucth.So next day when i picked it up i drove it around and not sure if it happens when engine is at normal operatering temp. but theres a wierd loose metal hitting metal, buzzing,rattleing sound coming from the rear end as u release the gas petal down shifting and acceralte up the gears just normal driving.Its some times happens and sometimes not.Someone on forums saying heat shields on the exhuast hiting and is something i can do myself? Also is true engine cant be rebuilt? planning to keep car long time. thxs