Chris, someone posted a whitepaper about the balancer tube connecting both chambers of the plenum. Varying the diameter has an effect on the midrange torque. I'm sure messing with this tube is going to take quite a bit of work.
BTW, I have the engine cover and plenum (with balancer tube, which is sold separately) looking for a new home. If I don't sell it, I'm going to put it on my car
