Hmm, Weber was pretty much upfront with the fact that their TB ports
were only for balancing idle and shouldn't be relied upon for accurate
readings at any sort of power setting. Perhaps the TWM port  is placed
differently than the Weber TB.

I'm still skeptical, but I can't think of any way to prove whether they're correct or not.  IMHO, I think your 42s should do just
fine at the revs you're turning. In fact, I think the intake charge
velocity created by the 42mm tract may help you. I have info here (not
in the attic!) reference intake VNE as well as a link to a calculator
for gas velocity in a pipe. The link is
http://not2fast.com/gasflow/velocity.shtml - you'll have to do the
metric/English conversion thing but the math is sound. I'll post the gas
velocity  thing later when I can get to the info. I want to say 600 f/s
but will confirm.
 
Neat calculator, but let's see if I'm using this correctly.  I'm looking at one rotor, since each TB bore and intake runner feeds only one rotor.  The displacement of a 13B is 1.3 liters, so one rotor is .65 liters.  My handy converter turns this into .023 cubic feet per rotor, per revolution.  Multiply this by 7000 rpm, and I get 161 cubic feet per minute.  I enter this into the gas flow program, leave the temp at 100F, and put in the runner ID of 1.625".   That gives me a mean velocity of 186 ft/sec.     From the notes at the bottom of the program screen, and your recollection of 600 fps, my 186 fps figure doesn't appear to be stressing my intake size at all.  The real question is- did I screw something up in the way I figured this?  Feeling better about my intake all the time.  Pity the area is covered with thunderstorms today.  I really don't want to test my new XM weather that bad :-)
 
Thanks,
Rusty (replacing home security system destroyed by lightning)