I had the same exact issue.
Essentially, each wire SHOULD have an individually stamped number on it. I believe in that subconnector that number is around the 500 range. They all go in numerical order.
When I was putting mine back together, the number stamped on slot 18 was "536." I was left with the two yellow wires like you. Only one of them was blank and the other was "538." Judging by all the other wires, which were all in numerical order, logic would dictate that 537 (first yellow wire) went into slot 19 and the second yellow wire (stamped 538) went into 20.
Now here's the kicker: One of my wires did not have the stamped number on it. Why? Im assuming that the ink came off when I removed the electrical tape used to install the O2 sims.
Double check carefully which yellow wire is stamped with which number. It took me a little while but I eventually saw it (should be about an inch down from the connector) and I was able to install it.
Best of luck.