Ok trying to figure alittle and can't get google to do it. Throttle body diameter= D where D=.85×(liters/cylinder×rpm peak power)^.5 or D=.85×(.325×8500)^.5 Part I don't get is (^). What does that mean? After alittle reverse engineering I found that a 40IDF is actually a 36mm max carb where d=venturi in d=(.7 to .9)×D or .9×40=36. According to weber flow chart a vmax needs 34mm nominal(35) venturi. So our stock carbs are pretty good then add vboost and intake tract velocities are excellent. Reverse engineer 30.5mm intake valve, 35.375 intake port calls for 36mm minimum venturi so 40IDF,s will work at max venturi dia. I would like to know what Prosnap is running? Numbers above are for my venture so insert yours into formula.