I highly recommend a scan tool. If you are going to use ForScan, they have 2 models they recommend. They are both by OBDLink. The Bluetooth model will link with your phone. The phone app will not program modules and is limited in function. I do not recommend the Bluetooth model for anything except reading data. I personally have both the Bluetooth and the wired versions.
Most plugs are "pre-gapped", however, I always recommend checking them. Think about how packages arrive on your doorstep. From the moment they are gapped on the production line, all through manufacture and packaging, during shipping and stocking, and up until the moment they are installed, they are susceptible to be changed.
These motors are direct injection and as such, no fuel travels through the intake system which allows the extra build-up of carbon from recirculated oil via the PCV system. I would suggest an intake/upper engine cleaning of some sort (SeaFoam, BG, CRC, etc.). Along the same lines, a fuel system cleaning periodically is good maintenance. When a motor is under high load, everything has to work harder/faster. Items that are beginning to have issues will usually show under load first.
A pending code is something that has not met the criteria yet to set a hard code. They are generally visible with a good scan tool.
Knock and misfire may be below the threshold to set a code or be physically felt but beginning to affect engine performance under load. I would check all the fuel trims, knock, misfire, etc. counts when you get a scan tool.
Fuel quality is a question because if you have not been using a top-tier fuel for an extended period of time, this may have led to build-up and deposits.
I would start with getting a scan tool if you are going to begin troubleshooting yourself. The next big thing is a service manual. Both of these will help you determine if it is a fuel, ignition, etc. issue and how to properly service it.
A KAM reset is a Keep Alive Memory reset. These are fuel trims, ignition curves, shift points, etc. Anything the vehicle uses to learn slight differences from your vehicle to the ones before and after it on the line. It also adapts to a certain degree to your driving style. If you do a KAM reset with no big changes, this may prolong your diagnosis. Usually, a KAM reset is done after a tune, large component changes, etc. By resetting the KAM, your vehicle will use a set of factory defaults until you complete enough drive cycles for the system to learn all the nuances of your system and driving. The vehicle will not feel or act the same until is has gone through it's complete learn cycle.
