Why not check out the sr20 forums. They use single and quad throttles on the same basic motor and I bet you can find heaps of threads about it.
As David has said- the time taken to empty the plenum is SFA...but even if it WAS a significant difference, who cares. Ditto with the engine sound thing. Once the motors running you won't care two shits what it comparatively sounds like.
Basically, don't end up like ME stressing over numbers on a piece of paper. It's a downward spiral into huge unfinished project territory and I owuldnt wish it upon anyone