From factory, the MAF sensors are located in the intake tubes (see attached). Where the MAF sensors might be on an SD tuned car depends on what you've got going on with the SD config. These setups are just what I'm familiar with. If not utilizing the MAF sensors in the charge pipes for IAT readings such as with the AMS IC pipes on my car, the MAFs can be removed completely. My previous GTR was relocated to the charge pipes for IAT readings (Pic attached).