Remove the computer controlled secondary throttle blades...

Many vehicles now come with two throttles, one you physically control, and one which the computer controls. For emissions, for fuel economy, for safer acceleration, think of this system as you asking for something, and the computer deciding when and how much to give you. 

For example, you want full throttle on a cold day, with a cold engine. If you simply whack open the gas, the motor will stumble, as the airflow that was trickling in at a steady velocity now has a huge gaping maw to rush down. As a result, intake velocity drops to near zero, the engine stumbles until the airstream eventually gets back up to speed in this new size of intake. Anyone with old flatslide racing carbs knows you can't just go to instant full throttle for this exact reason,

Now, give the computer a set of throttle blades. It's manifold sensor sees this rapid change in pressure, and it decides to shut off your ham fisted attempt by closing it's own throttle, then opening it at a rate of speed that allows  some semblance of intake velocity to be maintained. The result - better acceleration by a slower opening of the throttle.

But, now we can change things. My Triumph rocket three, a 2300cc motorcycle, uses it's computer controlled throttle plates to hobble it's power output in the first three gears as someone somewhere made the decision that it would be too much power to handle. I didn't buy a 2.3 liter motorcycle thinking it would be a gentle pussycat, I hope no one does. So, out come the plates, some fuel mapping to suit, a more controlled throttle hand, and it's an infinitely better motorcycle.

Also, stock MAP sensor maps are often confused by boost, so we'll just take them out of the equation.

Thankfully, the computer plates are the uppermost ones.  Use a WELL fitting screwdriver, heat if necessary, and patience to remove the 8 tiny brass screws. Also a very good idea to stuff rags ( I spray mine with a bit of chain lube for that extra tackiness) down the intakes. Anything falling should not get past the lower plates, but twist the gas and they'll open, letting that tiny chunk of brass go get intimate with a cylinder wall. Not worth it.