after 2 years of trying everything to cure my poor heater performance (is200)
i solved it by replacing my heater matrix with a recon unit
had it second hand took it to my local radiator repair guy
it took him 2 hours of constant flushing with a certain fluids to release all the crud
he stated that its almost impossible to complete the flush when the matrix is still in the car
installed it today 100% better its now as a heater should be
on both passenger and drivers side
i checked the flap on the heater box it self and it works fine (bye the way there is only one flap
i did that last year replaced cream with black what a difference
replaced the main carpet, seats, door cards, safety belts, and side interior pillar strips.