Buying a new maf sensor today. FOR MY my99 IMPREZA UK TURBO
Do you take the old one out and put new one in and then run the car is that it.

 

Its just a sensor mate, Plug and play.

 

think you need a special torx type screwdriver to do it though.

 

nope, 4 10mm nuts holding it all together if I remember correctly.
I had the battery off for an hour or so while doing mine aswell, just to give the ecu a chance to reset.

 

depends on the year, some are complete units and others you can just get the sensor part which is a lot cheaper

 

I done mine on saturday you need to undo two torx style screws then just replace the sensor, mine was done at power engineering and they did reset the ECU, dont know if you will need to do the same (mine was faulty dont know if that makes a difference or not) Hope that helps