I have a 92 Z w/ 5.7L engine. Car runs pretty well. No major issues. Spark plug wires get burnt up a bit sometimes and every 6 months or so I have a module go out.

Last few days car has idled poorly after cruising in the car. I start it up and it's around 12.5. As I drive down the road and come to a light it drops to about 8 and shudders a tad. After I turn the car off for a few mins and hop back in, the idle is fine. Only issue is after driving for a few minutes and then idling.

I just changed out 6 of 9 of the spark plug wires. 2 were cracked. The other 3 look fine. Plus, I can't get to them. Any idea what else the issue could be? The check engine light comes on sometimes while cruising, but will go off after awhile.

 

Car is starting to choke a bit while driving as well. Any ideas?