Maty, the Diff_FM is included with Modact 5.3, it's built into it, it's mot a separate mod that comes with it. so, you won't find a Diff_Fm folder, but the classfiles are included.
as for the malware thing, just ignore it - Chrome kicks out many such false malware alarms, and i can assure you there is nothing malicious in the Modact...
@ Fly, i think we might not be quite on the same page here, mate - i've said that i do hear a little wind noise when i open a canopy, but it's really quiet, and my main issue is that the engine sounds, which should also be louder, are suddenly almost whisper-quiet when i open the canopy.
no sounds are absent - it's just a weird, spooky near-silence when opening the canopy, when one would expect a heavy increase in wind and engine sound, it's just the reverse..
so, it's not as if there are no sounds, they are just extremely quiet when opening the canopy, when it should be louder, not quieter.
as for mods, i can post up a pic, but i'll just say there are many mods in this install, but they are all 3d mods, aircraft or objects, nothing to do with any sounds (other than the planes that have some of their own sounds)
i do have one mod installed that is a sound mod, this being stuka 40's environmental sound mod - this, however, also has noting to do with it, because i have the problem with or without this mod.