2011 Aveo: Check engine light keeps flashing.

[Khat]

I have a 2011 automatic Aveo sedan. One night back in the late fall, I think it was, last year, I took my mom's 4 labs out for a quick run three blocks to the corner store, and while I was in the store one of the dogs stepped on the Hold button. I didn't notice it until partway back, and there is a fair-sized hill in between the two places. Obviously, it reset once the car was turned off, and I realised why it happened, and everything seemed fine.
I should note here that this is generally a small town car. I usually drive it 4 or 5 k a day to get to and from work, with a max speed of 60 k. Occasionally I would take it out on the highway to get to the next town, or just charge the battery.
At the start of March my car started flashing the check engine light at me if I gave it too much gas, or took my foot off the gas to let it slow. (It took me a while to figure out the trigger.) This problem ONLY happens once I get up to highway speed, 100 k or above, and afterward will sometimes happen even when I slow back down to town speeds. As long as I ease it into the higher speeds it only happens once or twice for a few seconds usually, but if I speed up too fast, it happens more often. My sister put her checker on it, and it claims it's a cylinder misfire, and I took it to the local Canadian Tire for a diagnostic, and they said it 'might' be this one part that they claimed was broken because it was ziptied into place. Basically they had no idea and were just grabbing at whatever didn't look right. My brother, who is a registered mechanic, and who put the engine in the car the spring before, (the gasket was blown when I bought it,) says that that is not the problem, he ziptied it because it wouldn't 'snap' into place right. (He lives 4 hours away, so it's not like he can just pop over and check. I trust him more than I do the CT techs, though.) The spark plugs were also replaced, because we considered them the most likely culprit, and the starter coils were replaced shortly after the engine was. (He was driving it around all summer, I got it back in early October.)
I now work 2 nights a week in the nearby big town (a 30 minute drive) and the problem has not really worsened at all, after the spark plugs were replaced. The car doesn't lose power or make any odd noises at all, just flashes the light, but I've remembered that one trip and have to wonder if that did something to the transmission. I do know that the battery terminals likely need to be
replaced as well, as they don't tighten quite properly around the new battery's terminals, (the new battery is slightly larger, as CT did not have the right size when the old one went mid-winter and it was badly backordered, but everybody agrees that that's not the problem,) and the clock occasionally resets, so I don't know if it could just be that instead? I tried buying new terminals, but they are apparently not the right kind, so I'll have to take them back and see if I can find the right ones.

Edit: I just thought to add that it does seem to rev high after I've given it too much gas, getting up to between 3 and 4000 rpm a couple times and not wanting to go back down unless I pull over and restart it, after which it seems to be fine.

[Eg.h2o]

It could be just about anything. Bad wiring, bad voltage somewhere, oil dripping into the spark plug tubes……

[Khat]

I doubt it's oil in the spark plugs, because that should have been something the mechanic should have noticed when he changed them. I was mostly worried about the accidental hold screwing up something with the tranny, because, as I said, it does ramp up the rpms when it acts up.