Nothing has changed in the Fool's Gold mission files to change the frequency of ManPads. If there is a change it's likely to have been in Massi's updates.
Massi's Opfor pack has the following infantry groups (specifically African Rebels):
Fire Support Squad (8)
Fire Team (4)
Rifle Squad (10)
Sentry Patrol (2)
Team Anti-Air (4)
Team Anti-Tank (4)
Of these, the only units equipped with ManPads are in the Team Anti-Air (3 units).
In Massi's config for the units he will have set the frequency for the Anti-Air team to appear in @alive compositions. If all of the groups have been set equally we'd maybe expect to see AA appear 3/32 (~10%) of the time, but of course, he should have set this lower.
I don't know of a way to configure the @alive modules to disallow spawning (or reduce frequency of spawning) of one type of unit within a faction. The balance is down to the mod maker to get right and on this mod it may not be any more.
We could possibly run scripts to remove AA units, but given the complexity of doing this with @alive's virtual spawn environment and off-loading to HC, I'm doubtful it's worth trying.
What we need is our own Opfor pack......