Today’s word, 不正改造/FUSEI KAIZOU, is comprised of the words 不正/FUSEI (illegal) and 改造/KAIZOU (modification).
The 警察/KEISATSU (police) regularly block roads with checkpoints to cite cars for out-of-spec (in other words, unlawful) alterations to the:
* 車高/SHAKOU (ride height)
* マフラー/MAFURAA (exhaust)
* 触媒/SHOKUBAI (catalytic converter)
* 窓/MADO (window)
* 車体/SHATAI (car body)
* ヘッドライト/HEDDORAITO (headlight)
* テールライト/TEHRURAITO (taillight)
* オフセット/OFUSETTO (wheel/tire offset)
* など/NADO (et cetera)
Owners with violations are often issued a 整備命令/SEIBI MEIREI (fix-it ticket) and/or a 罰金/BAKKIN (monetary penalty/fine).
Check this previous post to see details on what’s legal/illegal in Japan!