sensors to the ECU harness without tapping anything else inside the engine bay. I saw the ECU schematic and there's a place to tap the A/F ratio readings and other stuff. I don't like tapping to sensors inside the engine bay. Thanks for any inputs.

 

If its a gage the ECU measures then yes you can tap it but its not going to be as acurate and there are several things the ECU doesn't keep track of like Boost and ETG and other things that you have to use sensors inside the bay.

 

The easy answer is yes.. I had at one time a AFR gauge for the narrowband O2 sensor.. I also tapped the RPM Signal for a shiftlight..

There are two things you need to keep in mind
1) by tapping these things, you can indirectly affect the values going to the ECU
2) The gauge/display will need to be calibrated correctly to the range in the sensor.

Bad news though..

The more common gauges you would want to install, don't have factory sensors.. For instance Oil Pressure is just a switch, not a sender. There is no true MAP reading (the MAF's Map sensor doesn't read any boost, since it is only used to calculate the outside air pressure/density) You can get air temp, coolant temp, rpm, Speed, injector Duty cycle (measured as PWM from the #1 injector) etc..