Welcome to the forum...
Most dealerships with a repair shop should be able to diagnose a defective coil pack pretty quickly, there is a special tool for just that purpose...
As for the throttle body, there are some diagnostics that can also be performed to check the function of the throttle body.

 

Hi psirangelo,

If a diagnosis is performed at the dealership, they will be able to find any present issues in your vehicle, and determine a course of action for the repair. If you'd like to send us your name, VIN, mileage, contact info, and preferred dealership, we'd be happy to set up an appointment on your behalf.

Amber N.
Chevrolet Customer Care

 

i had the exact same problem and spent a pile of money trying to fix that problem only to find out it was my intake manifold, the last two cylinders (closest to the firewall) the manifold bolts loosend off and since it is a plastic manifold it wrapped out a 1/4 inch and was sucking air. after paying another 1000.00 bucks to replace my manifold, my engine light has not come back and has never run so good.

hope this helps

 

I have a 2008 Express and for the last 2 yrs Im going through coils on my #8 cylinder. Any help??????