Worth noting that your Diverter Valve may also be split causing the boost tail off at around 4.5k.
Easy enough to check on the Edition 30's K04 engines as they're mounted at the top!
The piece at the bottom right corner of this picture with the 3 torq headed bolts on.
If you remove it, check the rubber diaphragms for splits.
Also, check the part number, if it ends with B or C then it may be worth upgrading to the latest revision.
People tend to go for Revision G as this is in all terms identical to the B or C however has stronger rubber. The Revision D is a piston style and is classed as an upgrade although people have reported them failing due to the piston not sealing correctly.
Another option is to opt for the GFB DV+, this uses the base of the original valve but with the addition of the DV+ on top.
Plenty of info on here, and TFSI Tuning on Facebook!
Edit; Just noticed your other thread, the part number for the Rev G is - 06H 145 710 G