It's "I'm a streetwalking cheetah", and "heart full of napalm", as per this interview with Iggy Pop from _Please Kill Me: The Uncensored History of Punk_.
Iggy Pop says: "I used to walk around London, through the park and stuff, with this leopard jacket I had, a cheetah-skin jacket actually- it had a big cheetah on the back-and all the old men in London would drive by in their cars and they’d stop and try to cruise me. All I liked to do was walk around the streets with a heart full of napalm. I always thought Heart Full of Soul was a good song so I thought, What’s my heart full of? I decided it was basically full of napalm."
So the Internet is correct in their listing of the lyrics.