I have a custom intake and was wondering if it matters where I put the mass air flow sensor in the tube. Can I put it closer or farther away from the turbo? I was wanting to put it about 4 in. after the intake flange on the turbo. Will that mess anything up or will the sensor even know the difference.

yes they can be picky as the turbulent air can alter the readings. i'd shoot for as close to stock location as possible. my Airaid intake has it in a seperate spot and it throws maf codes occasionaly..

The MAF sensor does not measure all the air only a portion of it, so you need to keep the tube diameter as close as possible to the original size to make it read properly and you would like to keep it in a straight section of the tube away from any bends.