Loud rattle sound - 986 boxster

[soxboy]

My 987 2.7 has just started making an odd rattle today. At first I thought it was the exhaust blowing (manifold even?), but it goes when the engine has warmed up. Having read this I'm wondering (and in many ways hoping) it could also be a heat shield, however I'm also wondering if it could still be the exhaust?