> Are there problems with the teflon-impregnated filters? 

I would say the same caution as Slick-50 applies.  See the Engine Oil 
Bible on the part about engine additives:

http://www.geocities.com/MotorCity/2195/engineoil_bible.html

BTW, I "treated" my '90 Eagle Talon with 1/2 bottle of Slick 50 
with one oil change a few years back before I knew better.  Now I'm 
trying to figure out how the hell to make sure that stuff comes out.  
Maybe some 0W50 flushing oil?  No problems yet though.

-Karl
Karl F. Bloss - blosskf@ttown.apci.com
'87 Vanagon GL  "Beverley"
http://www.enter.net/~bloss/vw/