1994 Sidekick RPM Question

[fixkick]

on 16v
air leaks (vacuum) cause lean , but id corrected by 02 sensor front (a ECU servo function) and goes normal
the the leak gets worse and o2 looses control (like most new cars) and goes way lean AFR air fuel ratio and engine slows down (for lack of fuel and attendant power)
this is 16v world.  here.
hot engine, and if closed loop works, then AFR is perfect, and minor air leaks are self adjusted.  
if the maf measures this air the MIX is always OK.
but if the vacuum leak is behind the MAF as all ARE. then it goes lean, if closed loop is lost. and engine slows.

normal leaks are
TV throttle valve.(drivers right foot)
ISC
IAC
bleed
and now others allowed.
all others are UNMETER AIR (means MAF did not measure it)  the guts are here, best drawing I annotated.
the EGR must not leak too.(it , the gasket or casing of it cracked)
many old cars leak air,(vacuum leaks) and the owners hide it by closing the bleed screw.
like a homes roof leaks so owner buys a bigger basement water pump. eeeek