Just a suggestion. Why not break up those 2 states into a few more states since they are basically way bigger than the whole peninsular with 9 states plus 2 f.t. This way, development can be spread more evenly since those new states will get their own specific budget to develop their states.

How? Well, since both states always claim that they are countries within a country, just raise the status of their division/districts into states with equal status to peninsular states while both 'countries' keep their status as countries within a country.

In this case, bigger is not better. The smaller the region, the more focus development can be.

If say Sarawak do get 20% oil royalty claim, I bet they going foucs thier spending on developed area more and less on other areas. By splitting it, Sarawak as a nation is obliged to give equal treatment to her states. Just a theory here.

For me, Perlis is actually pretty well developed for a small state with smallish population. Again, just a theory.