Beta Rho Greater Omentum. A high class and secret medical society, originated in Upstate New York. Members, also known as "bros", swear their allegiance to the greater omentum. Members have shaved chests, consume tacbros every Tuesday, and gather most weekends at the "frat" for party activities. Pledges must perform a self lobectomy, removing 3.14159265 (pi) ounces of their greater omentum as a sacrifice and sign of loyalty to BPU. Startups of other chapters around the USA are pending.
Hey Bro, you going to BPU tonight?
BPU is a term commonly used in the "tuner culture." This term stands for Basic Performance Upgrades.
Another use of the term BPU sometimes occurs when describing a vehicle - such as saying, "He's got a BPU Supra." When used in this fashion, the BPU is being an adjective and describes the car as having its (the car's) performance upgraded with basic parts.
BPU's mainly include exhaust systems, headers, downpipes, smaller-sized turbos, etc. (Upgrades that are not considered basic include twin-turbo systems that are not stock, boring out the engine, engine-swaps, nitrous, etc.)
Vehicles that are commonly referred to as being "BPU" are Civics (well..most Hondas), Supras, Evos, STIs, etc. This is one term in the "tuning culture" that is not limited to Japanese automobiles.