A clogged diesel fuel filter INSIDE the fuel TANK will cause engine power loss, as much as a clogged filter in the fuel pump in the engine compartment. The Toyota Innova D4D diesel has an additional fuel filter inside the fuel tank. Please see the pictures in the Facebook page "Toyota Innova Owners Phils". It was the solution that let my engine regain its power. Before it had difficulty even climbing a slight incline and could not accelerate faster than 80kph or 60mph. Cleaning the tank can be done at some gas stations or repair shops. It just cost me PhP750 or about $20.
Before I had replaced replaced the fuel filter (helped a lot when it was clogged, but later replacing it did not help) the SCV valve with a longer one (no improvement), cleaned the injectors (slight improvement), sprayed cleaner in the air passages (I think the throttle - no improvement). Only when I had the filter INSIDE the FUEL TANK (yes, there is a filter inside), then I regained the engine power.
Before I had replaced replaced the fuel filter (helped a lot when it was clogged, but later replacing it did not help) the SCV valve with a longer one (no improvement), cleaned the injectors (slight improvement), sprayed cleaner in the air passages (I think the throttle - no improvement). Only when I had the filter INSIDE the FUEL TANK (yes, there is a filter inside), then I regained the engine power.