After diagnosing the SEVERE LOW POWER complaint under LOAD in Part 2, we're waiting for eBay to deliver the OEM NOS ACDelco Mass Air Flow Sensor.

Meanwhile, let's focus on the ROUGH/HIGH IDLE/MISFIRE problem.
Lots of variables here.
Since the Olds has some questionable AFTERMARKET parts already installed under the hood, let's get a good baseline on the basic systems:

-Engine Mechanical: Relative Compression Test with Scope.
-Ignition: Spark Plug Inspection.
-Air Intake: Vacuum Leaks, Base Idle Speed, TPS adjustment
-Fuel System: Fuel Pressure, Injector Flow Test.

Some of the tests are very revealing...
Looks like we're definitely dealing with MORE THAN ONE PROBLEM, which is to be expected on a 40-year old vehicle!
Customer is anxiously awaiting the results, so let's GO!

S.U.R. & R. FPT22 Deluxe Fuel Injection Pressure Tester Kit:
https://www.amazon.com/dp/B004IJOLPE?...

OTC 3398 Fuel Injection Pulse Tester:
https://www.amazon.com/dp/B0002SR5OO?...

Enjoy!
Ivan