Easiest and cheapest things to do would be

1. Run a bottle of fuel system cleaner. I'd recommend Redline SI-1.
2. Clean your MAF sensor
3. "Dust out" your air filter
4. Remove and clean your ICV. While you do this - check for a tear in the boot that connects the air intake to the ICV.

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2006 X5 3.0L - Schwarz Black/Truffle Brown
Stock
But I keep it clean