For whatever reason, the factory and dealers use a longer length filter than what the generic parts store brands give you. For example, FRAM always points to a tiny PH3387A for almost every GM engine... which is the same filter that they recommend for 2.5L Pontiac 6000's, 3400 SFI's, 3100 SFI's, etc etc. I always ended up using 3940 or something like that which is a long length one that has the same diameter face, so it screws right into place without a fuss. If you're not using a Delco filter, just match up a longer filter with the same mounting face as the smaller one.