Thanks for the offer, but I had another offer and have some paxmate on its way.
I will have to take some pictures of what I have done. There is only one thing I can think of regarding the grilles. I originally taped the inside shut. I then opened it one slit at a time. However later I wanted to cover it again, so I used tape on the outside. The only thing I can think of is that somehow having a layer of tape on the inside and outside is effecting the air flow, even though both are cut through. I will have to remove the inner tape altogether for now until I decide what I want.
I will do some more investigating when I get home from work.