2006 Cadillac CTS changing spark plugs in 2006 CTS

You need to remove the shield, as well as the upper intake manifold.

Here is the procedures, the cross car brace mentioned, goes from strut towe to strut tower. If I am correct, your car does not have one.
Fuel Injector Sight Shield Replacement
Removal Procedure

Remove the cross car brace, if necessary. Refer to Cross Vehicle Brace Replacement .
Remove the oil fill cap.
Disengage the cover/shield from the ball studs by pulling up firmly on the rear and front of the engine cover.
Remove the engine cover/sight shield.
Installation Procedure

Position the engine cover/sight shield over the intake manifold so the grommets are aligned with the ball studs.
Press the engine cover/sight shield down firmly near the ball studs in order to install the engine cover/sight shield.
Install the oil fill cap.
Install the cross car brace, if necessary. Refer to Cross Vehicle Brace Replacement .

Upper Intake Manifold Replacement
Removal Procedure
Turn the ignition OFF.
Remove the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement.

Remove the air inlet duct. Refer to Air Cleaner Inlet Duct Replacement.
Disconnect the brake booster vacuum hose from the intake manifold.

Disconnect the purge solenoid valve electrical connector.

Disconnect the purge line (3) from the purge solenoid valve.

Remove the wiring harness retainer.

Disconnect the throttle body electrical connector.

Remove the upper intake manifold brace stud (1), bolt (2) and brace.
Disconnect the positive crankcase ventilation (PCV) hose from the right bank camshaft cover.

Disconnect the barometric pressure sensor electrical connector.

Disconnect the intake manifold runner control solenoid electrical connector.

Remove the injector harness bracket bolt.
Remove the left bank ignition coil wiring harness from the bracket.

Remove the upper intake manifold bolts. Some deflection of the cowl panel may be necessary to extract the right rear bolt.
Remove the upper intake manifold with the throttle body.
If the upper intake manifold is being replaced, disassemble the intake manifold. Refer to Intake Manifold Disassemble.
Clean and inspect the intake manifold. Refer to Intake Manifold Cleaning and Inspection.
Installation Procedure
If the upper intake manifold is being replaced, assemble the intake manifold. Refer to Intake Manifold Assemble.

Install a NEW upper intake manifold gasket.
Install the upper intake manifold.
Notice: Refer to Fastener Notice in the Preface section.

Important: Tighten the intake manifold bolts in an X pattern starting with the inside bolts and moving outward.

Install the upper intake manifold bolts.
Tighten
Tighten the upper intake manifold bolts to 23 N Â m (17 lb ft).

Connect the barometric pressure sensor electrical connector.

Connect the intake manifold runner control solenoid electrical connector.
Connect the PCV hose to the right bank camshaft cover.

Install the upper intake manifold brace, stud (1), and bolt (2).
Tighten
Tighten the intake manifold brace bolt/stud.

8.1. Tighten the intake manifold brace bolt (2) to 65 N Â m (48 lb ft).

8.2. Tighten the intake manifold brace stud (1) to 10 N Â m (89 lb in).

Notice: Ensure proper engagement of the wiring harness connector. The wiring harness connector must be installed straight onto the component connector and firmly seated. Visually inspect the connector to ensure that the connector latches are engaged and locked. Any damage to the connector or wiring must be repaired. Failure to follow this procedure can lead to an intermittent electrical connection, driveability concerns, and/or wiring harness or wiring harness connector damage or failure.

Connect the electrical connector to the throttle body.

Install the wiring harness retainer.

Connect the purge line (3) to the purge solenoid valve.

Connect the purge solenoid valve electrical connector.
Connect the brake booster vacuum hose to the intake manifold.

Install the air inlet duct. Refer to Air Cleaner Inlet Duct Replacement.
Install the fuel injector sight shield. Refer to Fuel Injector Sight Shield Replacement.

It is really not as difficult as it looks. You may not even have to 'remove' the upper intake, as much as just to move it to access the coils that are in interference. You would still have to do some disconnecting and fastener removal.