Did I just hear the sound of someone opening a very old can of worms? First of all the J-tubes: they are just like the innards of your old heater boxes so you won't see any change in economy or performance unless the diameter of the pipes is radically different from the pipes in the heater boxes - which given the ones that I know - they aren't. I run J-tubes on mine because I had no need for heat in a summer driven convertible. Performance comes at a cost. Just as no man works harder without using more energy you can't work an engine harder without paying a price in fuel consumption. Moreover, you are also using up the life of your engine trying to get that higher horsepower. The flat 4 was designed to run under stressed unlike other 4 cylinder engines of its era which were wound out at higher RPM's. Let the old girl lope along with a stock exhaust and a clean air filtre and it will maximize your mileage. Don't mash the pedal. Keep all of your engine tin in place to keep her cool. Keep your valves adjusted, your oil changed and your tire pressures at the recommended setting and you will have a happy bug. BUT don't forget - it will give you gas mileage good for a car of its era. Modern fuel injected four bangers have the higher horsepower AND better mileage through the miracle of modern engineering technology. Just be happy that you aren't driving a 455 V8 from your bug's era. I feel the pain of those who have collector cars powered by the big old iron 8 bangers! Ouch. Just my opinion. Dan (MY72BUG) in Goderich
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.