TwinTurbo flat spot?

I've read that there is a flat spot between 4000rpm and 5000rpm on the BH5 (1999 car) twin turbo Legacy GT-B. Is this correct and if so can it be ironed out?

Thats normal. Search Valley of Death ( VOD ) on google

It's normal, if the car has been mapped it will be minimised. Generally about 300rpm at most, it's a split second changeover when watching it on a gauge. I never found it an issue when accelerating through the revs. If you are flat out, you won't change down into it unless you short shift, if normal driving then there's no issue. The only time it would be a problem is if you are cruising behind someone and decide to overtake, if you change gear into the vod, power will drop for a second while the car sorts itself out. Other than that, they are brilliant cars, I'd love another as a daily driver.

As above mate it's not as bad as its made out to be, with a decent map it can be reduced but with driving the car you'll get to learn when to change gear to avoid hitting the flat spot