2000 Chevrolet Blazer Mass Air Flow Sensor

You need to remove the air cleaner outlet. Then you need to inspect the Throttle Body bore and the throttle valve plate for deposits, and you must open the throttle valve to inspect all of the surfaces. Finally, you need to clean the throttle body bore and the throttle valve plate using a clean shop towel with GM Top Engine Cleaner, P/N 1052626, or an equivalent product.

You need to turn OFF the ignition and disconnect the MAP Sensor harness connector. Then you need to remove the MAP sensor by pulling it straight up with a slight rocking motion. After that, you need to remove the MAP sensor grommet. Finally, you can discard the MAP sensor grommet.

No, you don't need to remove the upper Intake Manifold.