I think it's the gaskets on the Toyo filters - they are a hollow o-ring. When I've used another brand, say Purolator, with a solid rubber gasket, I've not needed to get them as tight. I do usually need to use a wrench to remove either kind - I use the kind that fits like a cap over the top of the filter. I also have one that is a square piece of pipe with a length of seat belt strap that I use when need be - it will remove even the most stubborn.

96 T100 Titan Xcab V6 2WD,Powertrax No-Slip Diff, buckets, mini-mods...
http://picasaweb.google.com/scott.broam/TruckProjects#