This is the first time I've ran a completely closed loop setup. Is it best to place the sensor before or after the joint where the dumptube meets the downpipe?

 

it doesn't matter metering wise but you want about 12" after turbo so to avoid overheating it (shortning it's life span).

 

I have mine in the stock location behind the oil pan as I have mine wired into the stock wire harness. Makes life easier.

 

So the extra exhaust gas coming from the dumptube will not affect the readings of the 02 sensor.

Right now the sensor is basically at the stock location right after my flex pipe. My air fuel fluctuates during idle even though I have tuned it right on with my AEM EMS. The idle is pretty steady, but I can see that the AF changing from 12:7-14:3 even after I have tuned it for 13.9 AF. Even with 02 feedback on, I can see it still fluctuating. It does not really make my idle fluctuate due to the fact the injectors like that AF range, but still..it should be rock solid at 13.9. I thought I had a exhaust leak or maybe the cheap flex pipe is causing my readings during idle to be off. Just trying to brain storm here.

On top of that my AEM Guage widenband reads .5 off and the gain and everything has been adjusted.

 

A little fluxation is normal but I'll put money that your idle motor is fluxating back and forth. If you log it I bet you will find it corresponds with your AFR flux.

 

So is there a fix LOL. My friend Hoa Tran at AEM asked me what my update rate was which I have never messed with.

 

Theres a few Idle feedback settings you can mess with to relax the idle motor. feedback rate is one, theres also a dead zone, and fb max/min etc. Theres alot of manipulation needed to fine tune your AEM idle.