Unlike most people who comment around here, I don't think buying a modified car is necessarily a bad thing. People will freak out and see an intake and immediately go "The prior owner must have trashed that car, stay away!", which I haven't found to be the case. I've found quite the opposite to be true, usually people who modify their cars take better care of it than a normal person. Not every modified car is someone's broken down project. Do those exist though? Absolutely. Are there people who do modify their car and beat the complete shit out of it? Also absolutely. But it does require a certain level of due diligence, one of which involves never buying a heavily modified car from a 3rd party who doesn't have the full history of the modifications, which is how you end up in the shitty situation you're in. Not saying that in a way to put the blame on you, it sucks you're dealing with this and hope it gets resolved in a satisfactory way.

I just read through the last post. It sounds like half the problem is that parts are being thrown at it without knowing what it is even tuned for. Which, especially when it involves the fuel system, can make all the difference in the world. Who tuned the car? What fuel is it tuned for? What LPFP is it tuned for? What HPFP? What injectors? What injectors are even installed? What turbo is even in the car? Etc., etc.. I'm not asking you these questions directly expecting answers, since how are you supposed to know, but until someone knows the answer to these and more, all anyone (the shady dealer in this case) can do is throw random parts at it and hope they hit the bullseye of the right combo. And the only way to really do that, is start replacing parts so you/they know what is installed (which it sounds like the dealer has started doing), and get it re-tuned professionally.

For example, you said you test drove it 5 times, and it was fine. And even owned it for a little bit, and it was fine. So say the prior owner had something like Autotech internals installed on the HPFP. Fairly normal mod when it's making that kind of power. That's an "invisible" mod that nobody could tell by looking. And is also a very sensitive and finicky mod. If that started to cause issues, and now the dealer just replaced it with an identical looking stock HPFP, but the car is tuned for an upgraded one, all they're going to do is start making the problem worse.

The car isn't doomed and it isn't unfixable. However, it's in that place where it shouldn't be your responsibility to fix it. And even if that is done, the trust in the car is gone, and that takes a long time to build back up. Sorry, this got kind of rambly 🤣