Deceleration Valve

[OldsFan]

My truck has a deceleration valve that is supposed to prevent backfires when you suddenly let off from mid or wide open throttle.  The problem is the high vac condition that shows up in that situation pulling in too much fuel and causing it to have an over rich mixture in the exhaust.

Well I know it'll backfire without the valve, but not one of the Olds motors I have had has a decel valve.  Now, I've only owned pre-emissions engines in the Olds family.  But the same circumstances should lead to the same high vac condition and the same backfires...

Still no Olds engine I've had has ever had a backfire on decel (some lean backfires from misadjusted carbs  ) even without the valve.  I know a lot of SBCs don't have the valve either.  How do other SBCs (and others) deal with that problem?  Does my 305 need it just cause of all the emissions stuff?