You're right, "datalogging", as I anticipate you're referring to, does track a lot more than just air/fuel ratio. "Datalogging" as you're probably referring to is the data that OBDII interfaces can spit out.
I agree, that's really cool stuff. I'm a Computer Engineer, and when I get a post '96 vehicle, you bet I'll be using some FPGA's to create a dedicated digital display of all of the cool bits of information that is available. But I wanted a 4runner, and that meant getting a 2nd gen, on my budget. So, OBDII isn't an option.
Fear not, you are not without recourses... if you want gadgetry and active information you can:
1) put in all of the sensors and do it all your self
2) Use the sensors you were born with... you can do a great job of keeping abreast of the potential problems in your car without things telling you if you're willing to do the work.
The problem is, the '95 and earlier computer just isn't configured to do what you want it to do using a non-proprietary protocol like OBDII. I don't like this answer much, and I'm taking route 1. I'm tapping the sensors that are in the vehicle and interpreting the information. My favorite part of the project is measureing the pulse width of the fuel injection, and figureing the gas economy on the fly. It's really quite a bit more accurate that way than the "fuel computers" on other cars that use other methods. But then again, I'm an engineer, and it's what I do. If you're more specific as to the information, I can help you find ways to get it and display it. If you just want the gadgetry, I can't do much for you.
