Why does my 2000 LS 4.3 4x4 have a Mass Air Flow Sensor, an Absolute Manifold Pressure, and Intake Air Temperature sensor?

Transitionally I thought the engine required either IAT and MAP senor, Or MAF sensor + RPM...what is the use of having both and which one is factored into the computer more?

The reason I ask, is im running so rich my blazer smells like a lawn mower...and I already replased the O2 sensor.

 

Short (stupid) answer: Because that is the way it was designed.

Expanded answer: A Mass Air setup allows for a much more precise control over the engine over the older Speed Density method of engine management.

Have a read through this Car Craft Article.