This demented, long version of I’m Eighteen is from the German TV show Beat Club. Scaring parents all across Germany.
The song reached Number 21 on the US charts and was released three months before the Love It To Death album. Possibly because the band were signed to Zappa’s Straight Record label, soon to be taken over by Warner Brothers.
This is also (allegedly) the song that Johnny Rotten sang at the (so called) Sex Pistols audition.