It is sad to see, that a good level of expertise is so hard to find these days
If you don't have expertise - please don't destroy other people's ideas and interests in making their cars more personal, custom and fun.
An engine is a pump - PERIOD. Power = Air/Fuel mixture - the more, the better, given the engine can withstand the increase in power.
The options are ALWAYS the same for every engine, it's just a question of expertise and finding the right person, who knows what he/she is doing.
The very first thing as some of you already mentioned is indeed legality, whether you're allowed (or want to for that matter) to have decat, ITB, race fuel etc. in the end, every mod, no matter how small, adds up and increases power, but not every mod is legal in your specific part of the world.
You also have to understand the mindset of the Manufacturers, when they produce a vehicle, especially if it's not an end of the line STI or R Type or AMG version.
1. Emissions - the manufacturer ALWAYS
looks on Emissions first, it is the highest priority, otherwise they cannot sell their product.
2. Fuel efficiency - the better MPG you get, the more likely the MASSMARKET will purchase your model, as everyone wants to save on gas.
3. Power - and only as the 3rd and last main priority is power output.
Now what you essentially do, is you shift Power to the first and highest priority - tuning in a nutshell.
Yes, some extreme mods will reduce the lifespan of the engine, but not going too extreme, with some minor changes frees up a lot of engine performance, giving it room to breathe, without compromising longevity.
Trust me, when I say, even the lowest Chinese manufacturer brand can produce a reliable 2L turbocharged engine with 400-500HP easy, they simply have a completely different goal in mind, so it is up to us, to personalize OUR own asset, with our own money when tuning a car/engine.
So that being said, for all N/A engines, the standard is:
Headers, exhaust, intake/runner lengths, lightweight pulleys, larger TB, tune
- again, often you have to do your own research on where, what and how, the cost, and what can be found in terms of parts, or where to manufacture custom ones.
The more extreme/expensive route for tuning an N/A engine after the mentioned above, is porting the head, camshafts and ITB (individual throttle bodies)
if you're into the sound, of course.
, or race fuel, is also to be considered.
Fuel injections, Fuel pump, Fuel controller
etc. need to be addressed as the modifications go.
That would be in the area of a Stage 3 tune (please don't start the "couch tune worriers screams" about "stages" and that they are useless labels)
Doing the theoretical research so far, I'm confident to say that going from 182HP to around 220HP is not impossible, given the fact that it is a larger 2.5L displacement in case of the Subaru Crosstrek Sport.
If we talk force induction, the easiest and cheapest way would be to bolt on a Roots blower on top - Eaton M45, Eaton M65, Eaton M62, Eaton TVS 410, Eaton TVS 1320
are easy to find options for 500$ used on eBay, Craigslist, etc.
Specifically supercharging, and not turbocharging, as it is fairly easy to do and not many changes are required - seeing some Youtubers turbocharging NA engines for thousands and thousands of dollars without lowering ratios and adding forged internals just to get so little in return in just mind-blowing...
Given the compression ratio, usually a factory N/A engine could withstand up to 4-5 PSI of boost just fine (with water/meth cooling you could go up to 6-7 PSI), which will result in quite the change, HOWEVER given the cost, piping/IC, sensor installment and the potential bottleneck of the transmission (CVT) the increased torque of force induction could be dangerous, but then again, people who came that far, probably already know what they are doing.
Also, not to forget wheels and tires, their weight and design make quite the difference in being "fast", as well as a potential LSD, along with changed gear ratios.
Final note: coming from a practical tuning background, I plan to do a stage 3 build with ITBs myself, currently waiting for the 2024 Subaru Crosstrek Wilderness to be announced.