How much of a diff does it make on the placement of the MAF to the intake manif opening ?
i see people put them in diff places in there CAI sys. is there a set distance it needs to be ??
I built a 4" CAI and need to put in my MAF

 

4" dia means you want 4" in front of the MAF and behind it, 8" straight section at least- with the MAF in the middle of that

 

You will also find, esp with the PCB style one, that its rotation is likely to matter. Worse, the closer to any kind of bend or other discontinuity it is, the more difference that will make. I've watched where a car would idle NOTICEABLY different as the MAF was rotated around while it was running.

 

I’ve seen that as well with mine, I played with its position until I found the sweet spot.

 

i have it mounted at 9 oclock, so it clears the hood . 6" in front of the 90 deg bend into the TB

 

You seem to be concentrating on what is after the MAF. As Arthur said, what is before the MAF is just as important, maybe even more important. You want as smooth as possible airflow entering the MAF, no turbulence.

 

its a straight shot from the large filter to the maf

 

don't forget that if you changed intake tube diameters, you'll also have to update the tune to account for the airspeed velocity change.

 

what do you change in the tune for a 92mm T/B from a 90mm ?

 

for the throttle body, i'm guessing maybe a little bit of responsiveness (but i ain't a tuner, so i ain't sure what they do to accommodate that swap).

but i was specifically talking about how if the MAF was previously installed in a smaller-diameter section of tube, then the new tube will have slower internal velocity due to the increase in volume for the same amount of air to transit... which will make it think you're taking in less air than actual (could run lean).