I know a lot of people on here have...if you're curious I would give it a shot. I have mine at 7%...I think it makes a difference. Makes it feel a lot more responsive...that combined with a ported tb makes the car feel better for me.
Throttle boost is the 2nd best feature of the device. It definitely improves driveability on autos and gets rid of throttle lag. I would recommend adding 11.5% - 15% if you're modifying the stock tune. The 91 tune has roughly 15% throttle boost built in. I keep toying back and forth between stock and stock with throttle boost added. At 11.5% with the stock 80mm throttle body, it does improve the driveability and gets rid of the throttle lag to get you going (throttle lag is about that 0.5-1.0 second lag where you push the gas but the engine is trying to figure out what gear and how much power to put down; it is also the same lag during deceleration when you let off the throttle and the engine feels like it is engine braking). It also smoothed out transmission shifts as if it were at the right rpm to shift in both auto and manual modes.
Here's some rough calculations between increasing the throttle boost % on the stock settings:
Throttle Boost (increments of 0.5% on the tuner) on a stock 80mm throttle body to simulate similar flow of a larger throttle body at part throttle -
82mm ~ 5.0%
83mm ~ 7.5%
84mm ~ 9.5%
85mm ~ 12.0%
87mm ~ 16.0%
89mm ~ 20.0%
All of that being said, there is a point where the stock 80mm throttle body will reach maximum flow and an aftermarket throttle body will outflow the stock throttle body (83-85mm have 10 more degrees and 87-90mm have 20 more degrees) and as mentioned, you'll be restricted by the 84mm intake manifold opening. For reference 392 Throttle Body - 82.55mm? Manifold 84.1375mm?
Also, if you use the 91 octane tune with 15% throttle boost built in, anything you add with the throttle boost setting is 15% + your addition.