When I switched to a 40mm FCR, I found that throttle response and low-mid power increased across the board.
However, I also found that I lost around a tenth on my 300' drag times.
Unsure if that loss represents loss of traction or loss of top end because of the smaller carb bore. My guess is a small loss of top end because my MPH also went down a touch.
All in all the quad "feels" faster across the board, from bottom to top -- but the drag strip timing system doesn't lie.
So, in the end - for general rideability - FCR = Good. For drag racing, do not expect it to help you much if at all.