IIRC on the non-ISO boards, FUD=99 just holds pwm @ 80. This may or may not increase rattling. It did for me, but you can try it. The ISO board has a more comprehensive rattle fix system allowing you to dial in a wider range of options.
'14 S5 DSG
'09 E90 M3 DCT (sold)
[Evolve ECU/TCU|MS Pullies|K&N drop-in|Test Pipes]