Dual MAF ( Dual Mass Air Flow )
To do this you need to have:
- APEXi SAFCII(super-Air Fuel Controller)
- Second MAF and Filter
- Dual POP elbows or Droolz
- Shielded wire
- MAF
- Solder
- heat shrinks or your preferenceI already had a SAFC2, and I have an extra MAF from my turbo donor front clip. I purchased my dual pop elbows and extra JWT POP from Clark at Powertrix.com. I ordered my shielded wire from SPLparts.com for $16 shipped. I search stores in town and could not find this wire, it is easy to just order from SPL instead of going on a hunt. I received my APEXi S-AFC2 from Ebay for $250 shipped new in box. Dual POP is not recommended for cars not making 400whp. Dual POP is said to add 10hp at a 400 hp level. Why Dual MAF/POP? So that the Low speed drivability hose does not have to be used. Also to meter the air flow a little more accurately. Plus is one more mod to add to your list for bragging rights.
But!, here are some results I could find from member z324u. La-Z-Link. Also heres a quote from TARGETZ "If the filter on the MAF side is more clogged then the filter on the non-MAF side you are going to run leaner. If the filter on the non mass more clogged then the filter on the MAS side then you will run richer." Made total sense to me. These instructions are for someone that has already installed the APEXi SACF2. If you have not installed the SAFC2, then use its supplied manuals and come back to this.
Recap on the filter and MAF install. This was tight fit with the Stillen oil cooler, but the way things are placed, the dual pop fits better than the single pop. The single pops filter element used to rub on the Stillen oil cooler, damaging my old element... With dual pop the coupling of the filters rest on the oil cooler.
Oddly anyone with the Jspec mesh grill knows that the mesh has openings in it at the top. The pop chargers slightly rested into these openings, as seen in last picture....
Here are some pages in the S-AFC2 manuals that you should take a look at to understand this modification.
This is exactly what were doing:
 Our car is a mix of these two illustrations:
 This is the Stock MAF wiring Diagram
There are 4 wires coming from the MAF unit its self, 2 power the MAF,2 are the signal and sig ground. The dotted outline represents the shielding around the MAF SIG and SIG ground. The MAF gets is power from the ECCS relay and grounds though the chassis.
B,C,D,E are these wires. ECU PIN 27 is B on the MAF, ECU pin 26 is D on the MAF. D/pin 26 is MAF sig ground. B/pin 27 MAF sig. There are two ground wires here please don’t get them confused, MAF sig ground and MAF ground. B, MAF Signal (ecu input from maf)
C, MAF Ground
D, MAF Sig ground (runs in shield with maf signal)
E, MAF Power With the SAFC you have to create a new B and D for the 2nd MAF, this is where the shielded wire comes in.
The second MAF simply gets its power from C and E by splicing into the stock MAF's connector harness. 
Sorry for making it sound so complicated but it is quite simple.
For SAFC2:
White = MAF input 1 (stock MAF)
Blue = MAF input 2 (2nd MAF) The shielded wire of the 2nd MAF runs to the ECU area, The shielded wire has two wires and a shield in it. Choose one wire for MAF sig and one wire for MAF sig ground. This is the 2nd MAF’s B and D.
2nd MAF sig (B MAF) = Blue SAFC wire
2nd MAF sig ground(D MAF) = ECU ground Heres me "splicing" getting power from the other MAF, this was just a mock up to make sure things were working and they did.
 Solder the 2nd MAF to the SPL shielded wire.
 Run the shielded wire however you want to, to the ECU area. I ran mine under the headlights, between the splash guards and fender wells and threw the washer fluid port. Then reached up behind the A/C blower and pulled it down. There is another hole that you can you at the lower fender that will go into the frame. I have a BAT cable, BC and wideband wires already using that hole and couldn't fit anymore.
 The SAFC comes with extra connectors The blue wire from the SAFC should have a male connector, Put the Female connector on your shielded wire B (MAF sig input), or solder if you wish. Connect the D (MAF sig ground) to the ECU's ground, or your existing SAFC ground splice.
Set the SAFC to this for Dual MAF dual POP, Single POP ECU:
dual MAF/dual POP/JWT dual POP ECU program:
sensor no. IN=2 OUT=2
sensor cal. IN=2 OUT=AVE dual MAF/dual POP/single POP ECU program (stock or JWT,ASHTECH ETC):
sensor no. IN=2 OUT=2
sensor cal. IN=2 OUT=ADD
Key On Engine Off, go to Sensor check mode on the SAFC2. Check the voltage values. If your voltage is reading 5ish volts then you have an open in your ground. If your have a voltage of ALMOST 0Vs, then you have an open in the Signal wire, OR your MAF unit it's self is not receiving power.
You should be getting a reading of .400-.550Voltes
Once your engine is on don't be alarmed when the Drivers side MAF is pulling more air, this is simply the IAC pulling air from the drivers side filter. If you have a drivability hose, you should feel free to remove it if you wish.
NA and TT MAFs are the same, one of mine is 1995 NA and ones 1990 TT. They have the same part numbers. Disconnect the Battery cables so you do not mess anything up, or at least have the key in off during this mod. This and other write ups can be found here.
La-Z-Link Dane F Miller
NA dynoed 207 RWHP 185.2 RWTQ & 14.668 QT
TT dynoed 340 rwhp 361rwtq (rebuilding) sgp block/ gms550bb 
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Dual MAF/Dual POP Write Up with Pics and wiring diagrams. - 
