Yeah, the Extraguard and Toughguard were by far the most restrictive of 16 filters tested by Brand Ranks. The PH and TG3614 were twice as restrictive as the best flowing filters (Wix XP, NAPA Platinum, Purolator BOSS), and hit the 12 psi bypass pressure at ~9.5 GPM with warm oil. That may be enough flow for many engines, but in some applications they'll be bypassing often, especially when the oil's a bit cooler. This might be the reason they rate them at 95% instead of the more standard 99% absolute efficiency. They might not actually hit 99% efficiency for any particle size.