The Swiftech Storms low performance does seem a bit suspect and thought a bit more investigation was in order so took it apart to check for any obstruction but could find nothing and everything seemed to be in order so put it back together and quickly ran the test again using one DDC 1T 10watt pump with the modded Alphacool top with 1/2" EK barbs in both block and pump and ran the same test on an original Cather solid silver Storm with the standard 1/2" barbs - repeated tests three times and took the average.

Swiftech Storm = 2.6LPM
Cather Storm = 6.3LPM

I wasn't able to duplicate the test with anything other than the standard barbs on the Cather block as they use a 3/8" thread and i don't have any barbs to fit it so could only do a 1/2" like for like test with the Swiftech