Terrible Gas Mileage. Why?

After taking my 86 out of storage for the first time this year, I have noticed a decrease in mileage. I get about 120-140 miles per tank of gas. I used to get about 200-220 if I was being nice and easy. I still drive it easy, and I can almost watch the gauge go down as I drive. I do not have any leaks at all. After I did all of the swapping, I still got a decent amount, about 200. I changed the plugs, plug wires, cap, rotor and coil. I do have the fuel pressure jacked up a bit, I cannot remember the exact specs, but it is not too radical to max out the injectors. I ran an OBD II on my car and no trouble codes came up. I thought maybe the O2 sensors might be shot but according to this, they are fine. What else would cause my mileage to go way down?

Engine Modifications:

1986 Ford Mustang GT

-Ford E7 Cylinder Heads, Ported and polished with a 5 angle valve job, and Performance Vassco Dual Springs, Moley Keepers and Retainers
-Ported Lower Intake Manifold off of a 1986 Mustang 5.0
-Upper Intake off of a 1993 Ford Mustang 5.0
-Mass Air Conversion
-1/5/8 Jet-Hot Coated Pacesetter Headers
-Kirban Adjustable Fuel Pressure Regulator
-Pacesetter Off Road H-Pipe
-Flowmaster 3 Chamber Exhaust
-65mm Ford Racing Performance Throttle Body and EGR Spacer
-3.55 Rear End Gears
-19 Pound Fuel Injectors
-Ford Motorport 9mm Spark Plug Wires
-MSD Blaster Coil
-Modine 3 Row Radiator
-180 Degree Thermostat
-Pro 5.0 Power Tower Shifter
-140 Amp Powermaster Alternator
-K&N Conical Air Filter
-ARP Head Bolts

Suspension Modifications:

-Tru-Speed Strut Tower Brace
-Tru-Speed Shock Tower Brace
-KYB Gas-a-Just Shocks, Struts and Quad Shocks
-Subframe Connectors
-Steeda K-Member Brace
-Eibach Lowering Springs
-5 Lug Conversion Which Includes 11” Front Rotors with Dual Piston PBR Calipers and Rear Disc Brakes
-1999 Ford Mustang Cobra 17” Wheels with Yokohama AVS/ES100 245/45/17 Rubber
- Maximum Motorsports Caster/Camber Plates

Yeah I just oiled my K&N last year. Maybe I will do it again since it sat all winter. But I doubt that would cause that much of a decrease. At least I hope not.