Hi Dekryptor,
I have been to Kinshasa twice and they did not check any of my belongings except passport and Yellow Fever vaccines, but just make sure you don't have any military photos or political stuff. I found them more thorough at Goma airport in the East,as they checked my cameras and asked if I was a journalist. Kinshasa is much more relaxed and there is less hassle for foreign visitors.
Regards,
Gerry
