In custom tuning I tend to see many cars today with mods that cause some type of leak, if its the exhaust design or air intake path.

This highly effects how the engine management adjusts the calibration incorrectly.

In searching for a automotive tool that injects smoke to track down leaks I found they cost around $1,200 plus so I designed one that would cost less then about $50 or even less if the parts are lying around.