Aftermarket Radio Wiring

I have a 90 GP LE coupe that I put an aftermarket Pioneer in. I got one of the conversion kits and plugs and hooked things up as directed. The stupid thing would not work until I tied both the red and yellow wires (supposedly hot and trickle power) together. Now it works but there is no power to it when the ignition is off and the rear speakers quit working. (they worked on the old radio when I did the swap) The only wiring diagram I could come up with for the GP radio was actually a 97 Grand Am GM shop manual I have for my daughter's car. The colors all seemed to jive even though the plugs were different. Does anyone have a 90 GP radio wiring diagram I can reference? This car also has the steering wheel controls.