BAD lean spot.... any suggestions??

One way to rule out the temp sensor is to ground it to the block and re attach that wire. It doesn't absolutely have to be in hot water to send a resistance signal to the ECM. I'm not sure what your ECM would use that signal for. Does your egr valve have a electric controller mounted on top of it ? I think 84 still used a ported vacuum switch only to take the egr in/out of operation. Either way to disconnect and plug that vacuum line will rule it out. I have had to hold the throttle in the sore spot and pinch vacuum lines with needle nose pliers hunting the culprit.
There are just so many little things that cause these problems. Even a faulty fuel vapor valve, electric or vacuum operated, can change the mixture.