OS swaps almost always have demons attached unless you are switching to another calibration intended for that same vehicle and hardware part number....
Do what Mike said. Changing stuff like MBT on a car that has long tubes and a flex tune is wild. Definitely doing too much. If the car isn't boosted...
Tuning can be complicated. There's a lot to learn, and it takes a LOT of time to learn it. Pay someone if your don't want to spend the time tinkering...