Just throwing this out there. Feel free to throw it back. lol!
IME, when it comes to modding a car, engine mods are the last thing to do. Cars come from the factory unable to properly handle the power they have. Braking is meh, suspension definitely sucks, and the driver is often the weakest part of the entire thing. The problem is, the driver is often unaware of how weak that part of the chain is. :)
I'll bore you with a couple examples on the racetrack. :) I have 380HP, yet earlier this year when I was at a track driving with a very experienced driver in a new Camaro with 640HP, he was about 1 second faster than me on a 2 minute lap. I was on street tires and he was on R-comps too. If I wasn't too lazy to bolt on my R-comps, I'd be faster than him.
Another time I was driving with a friend with a C63 AMG. He is a better driver than me, but I still caught him in 1/2 a mile, even with his over 500HP.
I read an article a while back about the Hellcat with its 707HP. The factory engineer who drove it at Portland International Raceway did a lap in the same time I did when I was very green and on street tires.
That's why my focus is on anything but the engine. Like I said, I'm just throwing this out there. :)