The following is an extract from the full article dealing with the history and tuning of Land Rover petrol engines. To view the full version, see https://graemecooper.com.au/petrol_performance.htm (available only on the desktop/tablet version of the website)
There is much misunderstanding about “tuning.” Essentially, this means making whatever adjustments / enhancements that may be needed to maximise the power output. The fundamental rule is that no amount of tuning will improve an engine that is not running correctly in the first place, so basic maintenance is an essential prerequisite. Additionally, delivering additional power means putting more strain on other vehicle systems, especially the drive train, steering and brakes so these MUST be up to acceptable standards before attempting to gain power. Also, power and torque are two different things and the objectives must be made clear before commencing.
Remember too that the engine typically delivers less than half of its power to the wheels. Every related system robs power so the more gadgets are running (like air-conditioning) the less power there is getting to the wheels.
There are, of course, many different stages of “tune” from relatively simple improvements to power and/or economy, through to tyre-shredding increases to power at the wheels. Money is the essential ingredient.
Graeme Cooper Automotive will provide advice on performance tuning to suit your particular needs and budget