Cadillac Repair: 1990 Deville poor mileage, rich exhaust no codes, spark plug wires, poor mileage

Question
I have a 1990 Deville with a 4.5 V-8 engine. The car runs rough similar to a fouled spark plug and has a rich fuel odor from the exhaust. I also experience sluggish power while driving. The service engine light has never come on. I have checked for codes from the ECM but did not find any codes related to the problem. What codes were in history were things like twilight sensor problem or disconnected battery. I cleared all the codes from the BCM and ECM. I drove the car in mixed driving conditions for over 100 miles and still have no error codes reported. Gas mileage averaged aroung 11 mpg. I have replaced spark plugs, wires, cap, rotor, air filter, fuel filter,PCV Valve and checked for loose wires and vacuum lines.I have also tested compression on all cylinders and it seems to be great - 145 to 170 psi. Fuel pressure is 38 PSI at idle and does not drop after I shut off the engine. Thanks for your help.
chipnbud@yahoo.com

Answer
Pull the spark plugs and see if any are carbon fouled and or gas soaked on one or more cylinders.

Start the car at night and after the engine warms up, Take a windex spray bottle and put water in the bottle and spray mist all the spark plug wires and see if you see any arching from the plug wires. If you DO, replace the wires.