Bad Fuel Mileage and gitting worse

[Fox*ak]

I have an 86 Chevy Silverado that has a 5.0l (305). Several months ago it started to get lower fuel mileage, it once got 15 to 16 mpg but has now depressed to about 9mpg. I adjusted the carb air/fuel mixture, put new hotter plugs in, and cleaned the K&N air filter but had no beneficial effects. After 30 miles with the new plugs I pulled them out and they looked good as far as a fuel mixture is concerned, but I still have black carbon looking smoke coming out the exhaust as if its running rich. I’m at a loss. It has an Edelbrock 550cfm with electric choke that is three years old, and the ignition is a new msd with new wires. The engine does not miss and still has a lot of power but worse fuel mileage and black smoke. Oh, it also has a new Edelbrock eps intake and no vacuum leaks on the intake or carb. Anybody have any ideas as to what else it could be?

[BoxWrench]

If you're seeing black smoke coming out then your plug reading may be a bit off. Black smoke means rich Fuel A/F ratio as you know...

The needles may not be shutting off fuel fill when at max and the extra fuel might be dripping into the venturiis and burning, causing the black smoke...just a first round thought to check...

[Fox*ak]

I tore down the carb and the needle and seats looked good but I noticed that the gasket between the body and top plate of the carb had a tear where the gasket goes around the air cleaner all thread. The gasket was still touching together but could have easily caused a vacuum leak within the carb. Do you think this was my problem or something else?