It seems once you help the FIB, you can never stop.

Drive to the Kortz Center.

Once there, go to the way point through the building to meet with Dave and watch the cut scene.

Now shoot your way out of the building.

It's the usual, cover, shoot, and move when clear.

The first chopper will appear and you will be automatically switched to Trevor.

Immediately shoot the pilot.

Now snipe the three enemies to your right.

You can now switch back to Michael or stay as Trevor.

If you remain Trevor, clear Michael's path so he can get to Dave. You will also need to take out the second chopper.

If you switch to Michael, head to Dave in the courtyard. Doing the usual, cover, shoot, and move when clear.

Once you reach him, a third chopper will appear, take out the pilot.

Now make your way to the parking area.

Once there, a fourth chopper will appear. Either shoot it down or steal a car and evade it.

Once clear, head to the way point. Trevor will be waiting behind the pawn shop in Morningwood. Watch the cut scene and the mission ends.

To get gold:
  • Time - Complete the mission within 7 minutes. Take out the fourth chopper, instead of running from it.
  • Headshots - Kill 18 enemies with a headshot. Plenty of opportunities for this.
  • Buzz Off! - Shoot down the pursuing helicopter. Once you get to the parking lot, use Michael's special ability and aim for the pilot.