Truck "chugging"

[1979C20]

On my 89 burb, a few nights ago the exhaust started "chugging" at a certain speed. Ot sounds like its missfiring. Then, after running like that for a bit the check engine light comes on with.code 44. Which is lean exhaust. So, besides fuel filter what could be possible causes?

[bd]

* a grounded O₂ sensor signal wire
* an open in the O₂ sensor ground
* a faulty O₂ sensor
* low fuel pressure
* water in the fuel
* (if used) AIR injection system pumping air into the exhaust system in 'closed' loop
* an exhaust leak
* MAP sensor slightly out of range
* faulty ECM