single plane intake on most efi's reduces the vacuum buffer. The plenum sees more pulses instead of a steady vacuum source. More LSA = steadier vacuum.
A little birdie told me.
Other things: reducing LSA closes the intake valve sooner shifting the tq peak down a bit. It causes exhaust tuning to be more crucial since more time is spent in overlap. Too much scavenging pulls raw fuel out the exhaust and too little doesn't take advantage of all the time in overlap. EGTs tend to be lower with less overlap.
Did I win?