I suddenly got the idea to make border relations for all municipalities in Rio de Janeiro state. During this work I discovered some problems in the imported border ways, and cleaned up where I could understand the problems. Still, Sao Goncalo and Duque de Caixas municipality borders are broken relations (not forming complete circles) as there was lacking and conflicting data. Also it seems according to wikipedia that the municipality of Novo Iguacu have been divided into two municipalities, though I have no idea where the border goes.
There are some people importing IPP data for Rio de Janeiro, maybe they can look into this.
Also the border between Rio de Janeiro and Sao Paulo states need to be looked at as they are two sets of borders almost maching.