Volvo 740 Air Matrix Issues

Hello all, ive been trying to fix an issue with my 740 gle for about 6 months on and off now and no matter what i do i cant get any air on any settings, blower is fine, vacuum bellows are fine (spent a weekend rebuilding the entire mixer box incl. new felt as a replacement for the sealing foam, refinished actuation rod, all tested and actuated properly. I've tried to take off the cover from the A/C evap and broke it accidentally but from what i can see there is a very small amount of debris which was removed easily with a blower. No idea what else it could be, any tips appreciated.