Need help with code 42 on Chevy Corsica

I have 1990 corsica 3.1L with 29k miles and it is throwing a hard code 42. It runs rough and idles too high when slowing down. When it comes to a complete stop, it finally kicks the idle down and almost dies.

I have replaced the following so far.

-IAC valve
-TPS sensor
-ICM
-Crank Sensor

I have checked these wires for continuity at both ends.

-#453
-#573
-#574
-#430
-#424
-#423
-#450 to ground

The SES still comes on after a few seconds of idling. I am wondering if the plugs, wires or coils would make it throw this code? I did check the coils at the secondary pins and I had something like 5.8#, 5.8# and 5.9# ohms.

I'm not sure what else to do and getting tired of spending money on non-fixes.