Power per litre

Hello. I like to design high power per litre engines, and have reached 2,000 horsepower per litre multiple times. But I was wondering how far you guys could push the limits.

My current best engine has a 1600 cc displacement, while making 3429.9 horsepower and 2477.5 Nm.

NA or turbo? Running nitromethane clearly. What about on premium gas?

It is turbo charged.