Better gas milage Guide,I am not selling anything here

I have a 1976 TVR thats a British Sports Car , The Car has a in line 6 cylinder engine . 21/2 liter size . 4 speed manual shift . Built back in the day when Gas was $0.40 a gal . The car was rated at 24 mpg . Who cared then .Power to weight was not to bad , only 107 hp. .The car weight is 1,950 lbs . The cars only problem was all the air pollution junk that really did not work right after a few weeks of driving or maybe to begin with. Thats the back ground . Now this same car gets41 mpg . and is much faster 15 sec 1/4 mile, A whole lot faster .Same engine . How was this done . Their is no magic pill you can drop in the gas tank and fix milage or any super spark plug that will fire up the fuelbetter. On the other hand I belive that almost any car or truck can do much better . A few years ago I got in a disagreement with a mechanic I worked with .I told him that I could make my car get twice the fuel mileage it was getting .At the time it only got 21 mpg. .He gave me such aWHO HA that the entire shop got into the act . I was so pissed off ,work started . One of the real keys to good milage is low end bhp or just power at vary low engine rpm . I am a indrustral mechanic by trade .Not just a person that replaces parts ,I repair things that you can't get parts for. But some things I will have done for me at pro machine shops ,I just don't have all the heavy machines . I tested a lot of things in my car ,and to be right on milage wise I installed another gas tank 1/2 gal .This was done for test ,I could run the tank MT on the freeway at 70 mph . and still keep on driving after the gas in the small tank was gone .Via Two fuel systems and a switch over . When done I knew how much gas was used down to the last drop . Unlike gas pump guess work . One thing I found out to my surprisewas Gas station cheating , Sometimes I would put 5 gal in the main tank stop and try to fill the 1/2 gal tank ,and wow at afew stations my little tank needed more filling . Right to the top of the tank is 1/2 gal and at one place I was not even close , I checked that place once more and the little tank was filled first. It was Ok like that . Then went back put 6gal in the tank and its wrong again hence gas station "steeling" . By the way I live in Ohio . Everyone in Ohio wants to move someplace else . Wonder why . This is a long story so I can't do it all now , But a few things that willdo vary little at least in my testare High fuel mileage rated tires Help -0, Types and brands of oil agian ZERO,Types and Brand names in gasZER0,wind turbulence device in front of the carb save your cash DID NOT WORK made things worse ,Oh and a magnet on the fuel line thats a good one !That trick never worked Bullwinkel ,You would need the power of a cyclotron to effect non magneticfuel in a split second when it passes the field (did try it just for the hell of it,did not work ) another Zero,Engine and gas additives (andsome if not mostcan do real harm not help)$20 a bottle colored mineral oil thats what most are big zerOto, And air dams ,unless you go 100mph don't mean much as well as so called low drag bodies10mph to 60mph almost ZER0. Now for a few things that will help ,Ram air system (forget the wind vortex device), Great cylinder head polish and design .(get a book on this one ) Improved bearings for the wheels ( I changed my bearings to Aircraft quality type, the ones I could)and high grade grease will help here,By the way bearings in the water pump are cheapies as well as other things like power steering and alternator .I also changed them to Aircraft bearings .Hard to do !Free flow pipes