[Piwoslaw]

Is that your A4 with the 350hp gasser still it, right?

Re: larger injectors - if you only swap them without reprogramming the ECU, then they may inject more fuel. If you are getting larger flow them it should be for a shorter duration. Though I'm not sure whether the injector swap would save you enough fuel it be worth while.

My 1.6 HDi also comes in 90hp and 110hp versions, the weaker getting slightly lower fuel economy, one of the reasons may be that it doesn't have an intercooler (diesels like a warm engine and cold intake air both for FE and power). I once saw a test where just adding an IC raised the power from 90 to ~100hp, while the other 10hp came from reprogramming the ECU to account for cooler air.

But if you'd be fiddling with the ECU anyway then might as well do an eco-remap.