emissions failure on 92 EJ22

I have a 85 gl wagon I put a 92 EJ22 in. It passed emissions fine the first year but this time it has problems. On the first test it failed both high speed and idle. I changed oil and replaced the O2 sensor and cleaned the plugs. The plugs and sensor were covered with a fresh layer of black soot that cleaned off very easily. On the retest it failed at idle, not as bad as at first but still over twice allowable on both HC and CO. I've just replaced the temperature sensor and cleaned the air filter (it wasn't too dirty so I just blew it out with compressed air). I can't find any intake or exhaust vacuum leaks. During the test the IAC regulated the rpm real close to 700. If any one has any suggestions I'd like to hear them. It will cost me for each retest.