997.1TT rough idle, P1522 Delivery of left fuel pump too low, help needed

[TT-Erppa]

Hi,

My 997.1TT runs rough idle at times, sometimes even stalls. Sometimes takes a moment for idle speed to stabilize after lifting throttle. Other than that the car pulls strong. ECU has been flashed, exhaust modified. Other than that stock. No fault codes except P1522, and that doesn't come back immediately.

I've looked at multiple correction of mixture adaptation values, they are 1,0000 and 1,0000 (B). Engine roughness values for cyl1, cyl 2, cyl 6 are negative values (-0,27 to -0,72), and cyl 3, cyl 4, cyl 5 are positive values (0,36 to 0,54).

Any ideas? Am I looking at any meaningful values, or should I look at some other values? If so, which ones?

Any help much appreciated! Thanks!