I can’t say I don’t disagree that you are ultimately limited by 3.5 liters.
It’s a relatively small engine for the amount of power it can produce.
My truck, tuned, some basic bolt ons.... is a blast on the street, but the power is a little twitchy and you know you are driving a turbo. I’m very happy with it.
I think that's the sweet spot for the 3.5. Tuned with basic bolt ons pushing 500-550 horsepower on stock turbos. Very efficient package with surprising output. Great bang for the buck. Beyond that, at least so far, I'm just not sure it's worth modding it. At least to me.