Where is the MAF sensor located? I am going to check to see if this is the reason for the sluggish multiple misfires under heavy load.

What year is your car? It should be located on the top of your throttle body.

Mass airflow or manifold absolute pressure sensor?

02 Mass airflow

Dan wrote an awesome guide:

https://www.gmforum.com/t278926/

Infact that reminds me I should have cleaned this when I was doing my tune up. Eh, I'll do it after I seafoam and change my oil and filters Wednesday.

Sam,
I just finally won a long battle with my Bonnie'* MAF sensor. What are the symptoms you're having? Any codes present? Mine was a P0102, and I troubleshot it for months, not wanting to buy a $200 sensor if I could avoid it. After cleaning it multiple times, cleaning my K&N filter, replacing the connecting wires, checking for vacuum leaks, and finding a leaky battery terminal I thought I had finally solved it. Then the CEL came on again... P0102. I finally gave in and replaced the sensor - problem solved. Gained about 5mpg city too! Just stay away from the remanufactured sensors from what I've heard. Oh, and it is located right next to your airbox on top of the throttle body, as Dan I think said.

-E