cleaner air package
That's a really good book about the introduction. Note the MTSC introduction is Dec '67. but some cars already had CAP. With '68, it looks like most all cars got it.
1967 Imperial & Chrysler CAP System Repair Book - Session 241
and more complete MTSC:
Master Technician Service Conference - Chrysler's Training for Mechanics
PCV was added much earlier - replacing the draft tube.
According to that booklet, the closed breather (hose attached to air cleaner) was initially a CAP item.
Most changes focused on idle and deceleration. Smoothest idle was exchanged for lower CO and HC. That meant leaner idle mixes. It also meant less initial timing, and reducing advance on decel for manual transmissions. Less initial puts more heat into the engine and exhaust (combustion starts later than it previously had).
Late 60s CAP carb idle specs are 14.2 AFR. These carbs tend to use air bleed adjustment instead of fuel restriction which allows finer tuning of the idle mixes, and less chance of the tech getting it too far out of tune.
