ecu questions

Ok ... I recently picked up a 98 gti vr6 (obd II) and go to get it inspected. It won't communicate. So I bring it home and test it with diagnostic tester... still nothing, the tester powers up ... but it can't talk to the ecu. so I pop off the connection port panel to check the wires. I find a red, yellow, gray and two brown wires. I managed to trace to gray to the ecu and confirmed continuity but couldn't do the same for the yellow. I assume the others are power and ground and they work fine.

Two questions:

If I pull the ecu, can I get it tested somewhere ... and how much might that run?

Second. is there a good schematic somewhere regarding connections to the ecu?

I really could use some advice ... thanks!