From what I have seen and my experience with the 3tgteu and other ljet systems you can use a toyota 2se ( the leaded version) air flow meter with no problems ( I have done this before ) from the measurements I made on bosch ljet ( they are almost all the same I know fiat stuff measures up good, and I assume that Volvo, BMW etc will work based on the fact that the pin out is the same from the ones I have looked at and they have the same VC and voltages. The resitors on the meter are the only things that change, but as I said I found no difference between a 2se, and the 3tgteu, and also a fiat one measuring at about ten point along the resistor curve.
After all the nippon denso/ljet is simply a bosch licenced l jetronic system. So all ljet sensors are interchangeable including the air flow meter from what I have found. This is why I suggest people use the 2se system if the want ljet on there 18rg or 2tg motors although a little primitive its readily avaliable and you get the same functionality as the original.