How To Get atleast 20 MPG in my 95' Grand Cherokee Laredo 5.2 V8 4WD heres what i got planned?

K&N Cold Air Intake, Jet Chip Stage 2 ( atleast the stage 2 3 would be better right? ), MSD Ignition, One Heat Range Cooler Plugs, 180' or lower Degree Thermostat ( i was thinking 160' Degree Thermostat even better right? ) , Conversion to E-Fan, run atleast 90 Octane Gasoline, I Already have a Flowmaster Super 40 Series Black Muffler with a Straigh Pipe in place of the Catalyic Converter ( which means No Catalyic Converter just a Straight Pipe ) im gonna do Headers but which would be best for Sound and Performance/more Fuel Efficient? , a Fresh Tune Up, and What is the Absolute Best Spark Plugs hence which would be the most Fuel Efficient? i currently use Chevron 5W-30 Motor Oil now my goal is atleast 20MPG City more on the Highway but the more MPG'S the Better Do You Think This Will Work? What are the Absolute Best Spark Plugs? the Vehicle is a 95' Grand Cherokee Laredo 5.2 mpi V8 4 by 4/4WD with a 152,plus miles running strong still i bought it over 2 months ago the stock rated mpg's are 12 city and 17 highway any helpful suggestions are greatly appreciated