I made a believer out of my landlord...He has a 1984 dodge pickup truck he uses for his properties...He had a garage work on it and as he put it, they took a few hours and tuneing it up and finaly got to carb adj. and timing where they used their timing lights, tachs, gauges, etc.With some carbs ears can be ok but with carbs with adjusting screws as little as a millimeter turn can be the difference between a good performance and a great performance. Sort of like setting timing by ear instead of by a light.
You guessed it, it ran like crap...lol...So I said I would be right over.
I had a wrench to loosen the distributor hold down bolt and a screwdriver for adjusting the carby...15 minutes later it ran smooth as silk for him...lol.
You can't really do this with the computer controlled vehicles these days but with old vehicles?...Hell yeah...lol.