I was assuming your base camshaft timing was correct
So, after resetting the timing belt (lined up correctly now) the problem was not solved yet then, right?
Not positive your Camry operates like a Ford but if the engine sees unmetered air the O2 goes lean
The processor adds fuel to make the mixture correct, that increases the idle speed
When the processor sees high idle speed and low TP volts it cuts some fuel to decrease the rpm
Then the process repeats and you get a surge due to the vacuum leak
Have you tried a bunch of propane at the rear of the motor both sides of that intake looking for an increase in idle speed?
Camry 4 pop with the intake in the rear is difficult at best to diag a intake air leak
The intake hose to the airbox is not cracked or split right?
That 99 has a maf and a baro too, right?