Vehicle is a '94 LT1 with 133xxx miles. Has never failed emmissions before. Finally got my overheating problem cured with an electric WP, the drive shaft for the mechanical was stripped. The idle is very bad (misses/general roughness) and it does the classic LT1 stumble till about 1000 - 1500 RPM then it runs fine. Opti was replace less than 2 years ago, all other ignition components except the ICM have been replaced within that time. Other recent fixes/testing are a new PCV filter, no vaccuum leaks that I could find, new intake elbow/IAT sensor. The #2 plug is darker than the others. Also the readings from the emmissions test are
HC in Grams/mile 2.13
C/O in Grams/mile 14.51
NOX in Grams/mile 1.27
What would cause both the failed emmissions and the poor idle. I've tried searching but can't find much on the combination of these two problems. I was thinking possible a bad EGR valve throwing off the mixture. The guy at the emmissions station said it probably failed because the A/F ratio is way off.

 

Well after more searching under the hood I found some cuts in the #2 plug wire, apparenty it was coming in contact with the A/C pully. The wire is still in one piece but the outer coating had some deep gashes in it down to the inner coating. I'm going to order a new set of wires. Question is would damage like this cause the engine to missfire only when it gets warm or all the time? Well I'll see what happens with new wires, although these are less than 2 years old.