Since this is dumped in the hole, is the term you're looking for "grachan"? From a Japanese retro car site:
"There are a variety of phrases used around the internet in relation to Japanese cars, it is perhaps worth an explanation of what some of them are and where they came from in order to understand them better.
The first is the most commonly used expression of Bosozoku, more correctly written as Bōsōzoku. It's literal translation is 'violent running tribe'. The term zoku at the end of the word denotes that it is a group or tribe, so you will also see phrases like vanningzoku and the like, which identifies something as being a group.
The Bosozoku have been around since the 50s and are traditionally a very anti social motorbike gang. They ride unmuffled bikes, with radically visible modifications, usually in a reckless way around city streets in large groups which usually have a uniform. The cars came along later but have been around since at least the 70's, they are similarly loud, very visible and anti social. The style of bosozoku cars varies wildly but they will usually have bright paint, radical body kits and preposterous exhausts.
The bosozoku style gets blurred into Garuchan or Grachan. Another word that can have zoku attached to the end, as in Grachanzoku. The word comes from the 1980's Grand Championship at Fuji Speedway, the car park was a Mecca for bosozoku. Here it became popular to have the more and more outrageous car styling inspired by the cars on the track. Some people will say they are grachan instead of bosozoku as they wish to avoid the gang associations and image of reckless driving."
