I know what you mean. In the early 80's I had a shop that had fish eye problems and could not figure out how to solve the problem. I checked every thing, washed and cleaned the both, changed filters. and checked the entire shop for any contamination. Nothing. Finally after about 3 weeks and the problem still persisting I climbed on the roof to look at the air intake system. I found 2 empty bottles of armoural laying beside the shaft that appeared to have been sprayed into the paint both intake shaft. After a thorough clean up the problem went away. It turned out that they had fired a disgruntled employee 2 days before the fish eye problem began....we could only assume. It just goes to show everyone how important housekeeping and the use of questionable products can be.. I ask allot of questions before I try or use any new after market product without the Okay from the paint manufacturer.