For Just a time period with this kind of outsized importance in auto lifestyle, "JDM" can be an acronym for a fairly uninteresting phrase: Japanese Domestic Market. It refers to objects built and intended for sale and use inside Japan (i.e., not for export). This contains everything from motor vehicles https://elevemotors.com/product/chevy-corvette-ls1-base-5-7l-v8-engine-transmission-loom-ecu/