One of the mags did a comparo on general performance mods the average bloke would do to his 4x4.
they used 3 commonly used and popular 4x4s. First they fitted larger exhaust to all and good gains in
performance and economy acheived, They then fitted a snorkle to all the 4x4. Now the engine was
getting cooler air instead of under bonnet temps again small gain in eceonomy.
It maybe in archives of 4wd Action/monthly, made interesting reading