BMW 750Li Engine Runs Rough

This Is A Purchase, So I Don't Know The History Of The Vehicle. I'm Not A Mechanic, But I Have Some Basic Knowledge. I Want To...

When I Hit Gas, I Hear A Hissing Sound Like Air And It's Running Rough But Cranks Right Up.

When The Car Is Cold And Started Up It Runs Really Rough For Approximately For A Minute And A Half And The Check Engine Light Is On But...

The Right Bank Of My Car Is Running Rough Or Cylinders 1-6. I Have Changed The Spark Plugs, Wires, Intake Manifold Gaskets, Cap, Rotor, And...