burble tune

A modification done to a vehicle, which intentionally causes the vehicle to backfire (unburnt fuel entering the exhaust). Unlike other forms of automotive tuning, a burble tune offers no gains in horsepower or fuel efficiency, and is in fact more likely to cause catastrophic engine damage and accelerate wear and tear.

Often done by teenage poser car guys who are too broke to afford mods that would actually increase the performance of their vehicle.

While a proper, high-performance tune may cause a car to backfire more than stock due to running more fuel and boost, a burble tune is specifically done only for the bops and bangs caused by a backfiring.

see also: ricer and rice rocket

Person 1: look at that POS GTI! It's backfiring like crazy, must not be running right
Person 2: nah, it's running fine, asshole just has a burble tune
Person 3: running fine? with a burble tune? Not for long...