NHTSA Complaint #11515704 — 2017 TOYOTA HIGHLANDER

Within 6 months of purchasing this car used at a Toyota dealership, the check engine, exclamation light, and "Go to dealership/check AWD" lights came on. I took it to the dealership who told me it would cost $250 just to check the lights. I took it to a car parts store who said "it's throwing a bunch of old codes". The dealership also suggested during oil change about $800 worth of work needing to be done and said my warranty I purchased would not cover it so I left. I had the fuel system flush done somewhere else.The lights went off for about a week and then came back on. About a month later.... While driving down the highway at a speed of approximately 60 mph, the rpm's and speedometer went haywire - jiggling and then decreased (and a weird sound like the car revving) even though foot was on gas, the car rapidly lost power and had to pull over on side of highway at night - this is of course very unsafe. Had to pull over and turn off car. Would not start right away but did after a few minutes. Took to mechanic - they could not find anything wrong. Could not reproduce. A few days later, after getting gas, car would not start. Had to wait an hour and then it did. Took back to mechanic, discovered water on spark plugs so had spark plugs replaced. Four days later, all the warning lights back on and car running roughly (like maybe lightly missing?). Component or system failure cause still unknown and yes it is available for inspection. Very frustrated and frankly a bit terrified to drive this very expensive vehicle.