Ford issued a service bulletin about some 01 and 02 2V engines that read:
"Mustang - Cold engine light ticking/rattle noise:
Some 2001-2002 Mustang GT and Bullitt with the TR3650 Manual Trasmission may exhibit a light ticking/rattle noise while driving after a cold engine start. The noise will typically occur between 2200-3500 RPM under light throttle (1/8 to 1/4 open) while driving. The noise may last for a few minutes (depending on temperature). The condition is due to the combination of light load operation noted above and normal piston to cylinder bore clearance present in the cold engine. To service, verify condition & reprogram the PCM with the latest calibration available via the just-in-time process if your WDS communicates with Fordstar. Also obtain calibrations on the Ford Professional Technician Society (PTS) website - select WDS then PCM reprogramming and click instructions for downloading... "
My 02 GT does this to a 'T' and it goes away when warm. To be sure, I hate my low-miles mod making this racket but since it goes away when warm and motor seems otherwise strong and doesn't use oil, it can't be that bad.
I think GMs LS motors tend to rattle like crazy when cold so us death-rattlers aren't alone...