The problem isn't that the 1GR-FE doesn't have enough power, it has plenty, as can be seen when you floor it.
The real problem is the throttle mapping isn't 1:1. When you press the pedal down 50%, the ECU equates that to say 30% throttle input. That combined with a TCU that never wants to invoke a downshift, or hold a lower gear, just makes the 5th Gen Feel slow in most situations. The 5th Gen tries it's best to keep you out of its power band at all times. In normal driving, I rarely see anything above 2000RPM, unless I really step on it. Then if you floor it, and actually get it into its power band, it will immediately upshift once you let off the throttle, even a little.
More power isn't the answer, and neither is a V8. The GX460 has the same horrible fuel economy programming as the 4Runner, and if you will notice, GX460 owners complain that it feels slow as well.
In all of the "Lack of Power" threads I have seen over the years, the actual source of the problem is missed, and people just want to throw HP or V8s at the problem, thinking that will fix their problem.
I have been looking at 2015+ WRX's lately, and interestingly enough, they have the exact opposite issue. Their throttle mapping isn't 1:1 either, but 30% Pedal Input will translate to 50% Throttle Input, which makes the WRX feel faster, but also cause drive-ability issues at low speed. Why can't auto manufactures stop messing around with ECTs, and just give us 1:1 linear throttle input?
I still could use more power. Even when stomping on it to get onto the freeway, I feel it can't get out of it's own way sometimes. Of course once again, coming from driving the wife's Outback which was really quick for that kind of car and had good torque, it's going to feel slow. You are correct about the MPG strong tuning on these things. My FJ feels like cold molasses driving around town most of the time. When I do stomp on it, it will down shift (eventually) and scoot pretty good for a big fat truck. It sucks on hills when I it runs out of power, but we can always slap in down into 4th or 3rd and it crawls OK.