Ryan,

A wideband O2 sensor will tell you the air/fuel (AF) ratio. An older O2 sensor (like the one on the car) varies voltage from 0 to 1. 0.5 is the calibrated setting for "perfect" AF ratio. The computer gets that signal and sends a signal (current) to the EHA to vary pressure to maintain that "perfect" AF ratio under "closed loop" conditions (no or little engine load). The AFX is an NGK brand of wideband O2 sensor that outputs a voltage from roughly 0 to 5 volts (perhaps 1 to 5) and has a chip inside the display to convert that input voltage to a number we can understand. 14.7 being the "perfect" ratio for no or little load running and 13.x being the "perfect" ratio for making power. As an aside, forced induction motors may be tuned in the 11s at max boost to keep "things" cool.

I too started the "other" way and after chasing the "problems" spelled out in the literature, I came up with my last post in the "CSI-E Tuning" topic.

I had issues with the wiring AT the connectors. The copper is probably brittle and green. In some cases, I cut about an inch off the wires at the connector and re-soldered. This is why I suggested that you check the sensors AT the ECU connector. Find a helper and have them wiggle the wires and see if the signal changes. I bet you find that at the CPS.

I have not had that issue so I do not know if the CPS will cause your poor mileage, but I suspect not.

It is VERY easy to check your idle microswitch. Remove the air filter and you will see it on the throttle linkage near the firewall. If you have the car running at idle, pull the throttle cable just enough to move the linkage away from the switch. Any change in idle? Yes, MS okay. No, turn car off and check for continuity at the switch. Nothing? replace switch. Working there? Check at the ECU. Not working there? Check your wires. Working at ECU, MS fine, time to check the Idle Air Control Valve. With car running pull plug at IAC valve. Car should die. If not, check continuity at ECU. See a pattern here.

Lots to do, sorry. Once you are sure the wiring is good, we can get your AF properly managed by the ECU.....after you check and match your injector flow rates. There really is no shortcut, but at $4 per gallon the time you take now will pay off nicely in the year to come.