Im confused

[Element816]

So in my 90' 525i, with the a/c off I have a rough idle, however when I turn my a/c on the idle balances out and runs fine

Any thoughts?

[BavarianFanatic]

Vacuum leaks. Idle gets a boost when A/C is on. It's probably just enough to compensate and smooth it out.

[Element816]

Which means I have a small leak.... Somewhere....