Just to clear up a few points:

Adding an intake etc might result in more air, but it doesn't lessen the fuel. The ratio drops because there is more air. Infact in closed loop the ECU sees the extra fuel and tunes accordingly so it actually increases fuel in some circumstances.

The major difference between the S-AFC and V-AFC is the S and V. The S stands for Super (because the JDM love superlatives), the V stands for VTEC. The V-AFC is an S-AFC with VTEC control.

The V-AFC doesn't directly add or subtract fuel. What it does do is increase or decrease the MAP (Manifold Air Pressure) signal. The assumption is that the ECU will see this and increase or decrease fuel according to it's maps. In small incremements this is resonably accurate.

The idea that the V-AFC can't add fuel is out of context. It comes from people trying to use the V-AFC for tuning in forced induction. With a turbo of SC set up the MAP signal is already very high and has to be capped so as not to send the ECU into limp mode. Once the signal is capped the V-AFC will no longer have an effect on it if it's upstream of the MAP signal. If it's downstream then it will be changing the capped maximium setting and will result in the ECU going into limp mode.

 

I agree with everything you said but this. You don't have to be FI to force the ECU into limp mode with a V-AFC. If I tried to add more than 4% fuel at certain RPMs (NA) the ECU would flip out. The "resonant humps" caused by my AEM CAI caused the AFRs to go lean enough that I was pretty limitted at how rich I could go. If I tried to tune for 13.2:1 across the entire curve, I couldn't do it with an AEM CAI and a MAP altering device.

 

Is anyone selling a harness for a 04?