Hi,
I have finally discovered the reason for power loss in my Innova diesel - the culprit is clogged fuel filter INSIDE the fuel tank. Of course you should make sure your fuel filter in the fuel pump is clean.
I've had long standing power loss or low power in my Innova D4D diesel van. I had my injectors cleaned, replaced the SCV valve, etc. I have also been using the Shell VPower diesel to improve power but cleaning the fuel tank made all the difference. Somebody recommended cleaning of the fuel tank which I had done at a local Shell gas station for P750.00. Try this as a first resort if your car has run many thousands of kilometers or you use gas stations that may have dirty fuel..