Keep those great posts coming! You have experience with the CVT based Spark, which I do not. So I learn from your posts. When I was (much) younger and had houses with garages, I have done everything DIY from brake jobs, tune ups, oil changes, coolant flushes, belt replacements, adding extra fuel filters (those tiny bronze fuel filters in GM cars get plugged up easy with bad gas), changing snow tires (necessity in Chicago driving). That in-line see through fuel filter instantly diagnosed why my car would not start on a cold evening in Chicago after work. There was no visible flow of fuel!
Without boring you, once I am driving home from work on my 25 mile one way journey, and my Chevy Nova starts to eminate hammering sounds from the engine. I had may be 70k miles on the V8. I pulled into a GM dealer, driving very slow, and 2 mechanics played around with my engine problem, and told me my rod bearing was broken, causing the very loud hammering sound. The remedy was basically complete engine overhaul. More dollars than my Nova was worth. It was Friday evening, and I decided against the repair. The mechanic advised me not to drive home, another 15 miles. He said if I tried to drive it, the piston rods could break through the engine block.
So I drive home, as slow as I could. The noise was more the faster I went. At home on the weekend, I read through my car manuals. I found out that if rod bearings are shot, the sound will be louder when accelerating or decelerating, because of the gap formed between the piston rod and the bearing. My engine was making sounds directly proportional to speed. Less speed, less sound. More speed, more sound. So I concludes it was not the rod bearing. My best diagnosis based on that very good car manual was bent or broken rocker arms. So Monday morning I drive to another dealer, a Buick dealer, and told the service writer, to check the rocker arms. After only 2 hour wait in the lounge, I hear my name announced and I walk up to the cashier, and she hands me the keys to the car with the bill. The problem was a bent rocker arm, and the bill was exactly 1/20 th compared to complete engine overhaul.
I have more stories like this of incompetent/shady mechanics. I learned quickly never to walk into a repair shop by saying "there is problem in my engine or transmission". Read a good manual, and determine what the problem really is. The mechanics are pretty good to fix the problem, after you diagnose it for them.