I had a 1996 and I had to clean the carbs one year after a long hibernation.
I am sure that you know some of this... but have to say to be sure.
On some of these bikes you need to remove a cover over one on the adjustments/jets do not remember very long time ago.
Have you done this area?
If your foam disintegrated... could there be anything blocking the intake tract?
Sitting thinking... reverse blow through all of the passages? I am sure you have done this too.
Yes the idle passages are very small. I feel for you. Time consuming job.