I bought a DIC and installed it on my 91 GP I got the wiring definitions here:
http://pages.prodigy.net/gearhead43/DavesGP/page12.html

Everything worked OK except for the fuel, in the page it says pin #B6 is for the fuel sender input (purple) I took it directly from the trunk but the DIC always says Chek Fuel when I press the range button.

Also the average speed is always around 128 mph which is insane, I took the speed sensor signal from the tranny.

Hope someone can help me out.

You can't use the speed sensor signal from the tranny. You have to use the speed output from the ECM. It should be an orange wire, but I couldn't tell you which one. The speed is calibrated in the ECM and translated into a pulsed signal to the speedo hud cruise etc.

As far as the fuel input, I would trace the fuel guage input to the dash and try that one. You may have gotten the wrong one from the sender.

You could use the VSS from the cluster...dark green wire on mine.