you need the AEM UEGO wideband O2 sensor to really get a good A/F reading... the Stock O2 sensor is worthless for tuning, and the AF guages read off the stocker... and thats a 0-1v range... narrowband. wideband reads from 0-5v, so its pretty accurate. WB 02's are expensive though, its sophisticated shizzle, stuff that MKIV supra guys use.

you could also check it on a dyno and use the WB o2 sensor on there.

the beleif that Neons, 2GNT's, and DSM run rich from the factory doesnt really give you much room to work with... its just a safety net built in, not enough of a margin for you to be tryin to bump the power on the stock fuel system... Returnless fuel ssytems are a joke, and cant flow enough fuel to support big power.

anywho... WB 02 is the way to go, like DIY-WBO2 or the AEM UEGO.

Oh, and a bigger TB and Intake manifold arent really the best way to get more airflow. more boost is the best way, within reason.