I would say most of my experiences were doing Driveability Problems. Driveability problems consists of for examples, a car comes in missing, hard to start, or no start at all, bad gas mileage, Check Engine Lights, you know the hard stuff. lol
I was equipped with scanners, lab scopes oscilliscopes,volt ohm meters,and the 4 Gas reading machine which measures the amount of pollutiants coming from your tailpipe. It is also a good Diagnostic Tool.
I really enjoyed the days of rebuilding the C-3 carbuerators back in the day! Now I think they left around 1984-85. This type of work was really rewarding to me. I could see the before and after results of my carbuerator rebuilds.
But let me get back to the point. I cannot believe what a tuneup consists of these days! In my opinion, its just changeing your sparkplugs for $80. Higher on some models! Of course thats when the mechanics have your car in the shop and looks for somthing else to Increase their Ticket averages.
I knew one shop who gave away a Big Screen TV just for selling the most parts for that month! It wasnt me. lol
So in short, when you go in for a tuneup, take your time and ask for the list of the Items they want to sell you. (with estimates) And do them one at a time. Unless your well off or going on a trip and need it all done today. Some services may be legitimate but then others may be just parts thrown at you to increase ticket averages. This Tech. most of the time will do a good job. Thats the guy who will win the Big Screen!