One thing to consider might be changing your priorities for the car, and refocusing on what it does best. The car's main strength is its quick and agile handling. It was never meant to be a crazy fast car in a straight line.That said, I find the stock power to be satisfying. I added a satisfying extra bump of power with the Mountune MP215 tune, and I'm happy with it, it hits a sweet spot for me.Continuing to chase huge power in this car,which it wasn't designed for, can be a recipe for dissatisfaction.
It might be that if you refocused on how fun it is to drive with the go-kart like handling, and how well balanced it is overall at a ridiculously cheap price, you might start finding it satisfying again.
If you're wondering if I have experienced a truly fast car, the answer is yes. I came to this car from an E90 M3, a 414 horsepower V8 with a nutty 8400 RPM red line.That car was really fast, but the problem for me was you couldn't really enjoy it without getting into illegal territory so fast.If I have a car that can go zero to 100 in about 10 seconds, I want to go zero to 100 in about 10 seconds.
I'm a mostly retired lawyer who has handled thousands of traffic tickets.Here in Central North Carolina where I practiced, every county has a point for a speeding ticket after which they won't plea bargain anymore. That speed is generally around 95 to 100. This means if you get a ticket going that fast, you're basically stuck with it, the DA will not reduce it. The consequences are then losing your license for a year, and maybe getting a limited driving privilege to drive to school or work if the judge is in a good mood. Your insurance also at least quadruples for 3 years. Do the math, that's a lot of money.
I'm also not interesting in pushing huge horsepower out of my car because it appears that it can handle up to 300 horsepower without compromising reliability too much. After that point, it becomes more problematic.It also avoids the situation where you're going 60 mph, you punch the gas, and in about 4 or 5 seconds you're going 100. At that point if a cop pulls you you're pretty damn screwed.
This is just something to consider before you take the drastic step of selling the car because it's not fast enough for you in a straight line.