87 GMC Code 44, how to fix this problem - GMC Cars & Trucks

Code 44 is a lean system:
O2 Sensor defect or system vacuum leak
1- Engine running
With WD40 spray on the engine:
Every Vacuum Hose, intake gasket etc... You will find the leak when the RPM change the sound. This will be your leak.
2- O2 sensor:
check o2 sensor connector for bad terminal
3-check this link: https://repairpal.com/gm-obd-code-44

Hope it helps.