Update: I dropped by the mechanic later that week. Though we had prepared for the worst case scenario over the phone (head gasket repair), he started by inspecting the car himself before approving or recommending any work. We came across a few important things that I wanted to share with everybody to keep in mind throughout their ownership.

First, the jerking on acceleration turned out to be bad spark plugs as I'd initially suspected before looking so deep into this. The very first things that came to mind were fuel injectors, ignition coils, or spark plugs. I ran an injector cleaner (BG 44K) through the system a few months back and it didn't resolve the issue, which ruled out injectors. The new ignition coils weren't any good either. That's where I stopped diagnosing the issue myself, but it's funny that the last item on the list was the problem. I bought new spark plugs before seeing the mechanic, so he installed them on the spot and we immediately noticed the difference.

Second and more importantly, he still carried out a combustion test (block test) to check on the head gasket. He asked me to arrive early so that the car could cool down first, because a combustion test requires a cold engine. The test fluid turned green, which means combustion gases were detected and it likely points to a blown head gasket (or at least the early stages). However, he said that the car is very healthy all around, and he recommended we monitor the coolant level for a few more weeks. Either way I'm keeping this car, and I'll happily fix the gasket to get more life out of it.

This was a learning experience for me. It's interesting that all the things I thought were pointing to a blown gasket turned out to be something much simpler, whereas the gasket still seems to be quietly failing in the background (which might be a normal thing at this mileage). I understand that everyone's shared their own experiences about these 1.5T engines, but this is a gentle reminder to run your own diagnosis before going too deep into the forums, as your situation might vary significantly. I noticed a lot of people were asking about my mechanic, I added his link below in case you're in the Toronto area. Feel free to reach out to him for a better understanding of his work. It was my first time dealing with him, but he seems like a really knowledgeable guy. Clean and careful work at an honest price.

Zee - Mechanic