If I use your max flow number(454) PM shows 124.37VE and 1138hp/848.9tq.
If I use 425/.700"lift PM shows 118VE and 1065hp/812tq
If I use 394/.600 lift PM shows 111.24VE and 987hp/758tq
Looks like pipe diameter is 2" with the 394 flow and 2.146 with 454 flow number.
Hope that helps. If ya have a specific VE number let me know. Only takes a minute.

http://www.youtube.com/watch?v=aIxaesJ190U

http://youtu.be/lCZAaN7fFLg