Ok so I found the possibilities:

Fuel Pump insufficient flow/pressure
Fuel Feed line clogged leaking
Fuel Pressure Regulator stuck open
Clogged Fuel Pump/Injector
Gasoline doesn't meet Owner's Manual spec
Deteriorated Primary HO2S sensor
Valve Clearance
Exhaust leak

So, damn, where do I get started?

And is there a way to know which one of these it is?