Extremely high. My estimate is it was 140+. Lolorito would have made it to Mensa - if it exists in Eorzea - with flying colours.
Why so? Because we know the IQs of the other members of the Syndicate and they pretty much reflect the internal pecking order of Ul'dah.
https://i.ibb.co/rfskMtM/Picture1.png
Note that a) everyone except Raubahn Aldynn had IQ of at least 1+ sigma higher than average and b) 66% of them had Mensa-class IQ (over +2 sigmas).
Everyone also considered Lolorito a genius. When narcissists like Teledji Adeledji and professional scholars like Dewlala say so, they recognized Lolorito had an equivalent, if not higher IQ than they themselves had. Lolorito was a voracious reader, he had a 3000+ books in his private library, understood Sil'dihn script, and he had tremendous appetitite for knowledge and he could lead a discussion over just any topic imaginable.
Knowing also what kind of a snake pit the Monetarists were, if Lolorito had had lower IQ than his closest confidants, he would have been ousted quickly. Men like Teledji Adeledji were keen to realize any weaknesses on any of their rivals, and exploit them.
These test results may come to the royalists as a terrible surprise. They expected the monetarists to have similar IQs as common thugs. When it turned out they were academic top level, it was against all their expectations. The monetarists were not thugs, they were evil genii. That is why they manage to control much of Ul'dah's internal affairs, supplanting the sultan in all but name.
This also demonstrates well how IQ is a completely amoral thing. It is the great enabler, nothing else. Top-high IQ can create Louisoix, but it can also create Lolorito.