'89 200 check emissions light

[Keith Lawyer]

I posted last nite w/problems w/my 200 dying.  Today
cleaned the ISV and problem seems to have disappeared
but I'm still skeptical.
  Anyway, as long as we've had the car (about 1 mo)
the check emissions light will come on.  First time
happened during overboost (which is another problem I
have yet to fix).  Tonight during my test drive, after
driving around for about 20 min to warm her up good, I
started really getting on it (for me), like 5k rpm and
slightly above.  Sometimes it would overboost and
sometimes not.  That's normal- relatively speaking-
but after that the check emission light would light up
everytime I'd get above approx 3k rpm, regardless of
how hard I was accelerating or boost.  This is the
first time I've seen it come on w/such frequency and
regularity.  It would go away once I would depress the
clutch and shift until about 3k rpm in the next gear,
etc.
  Do you believe this is it's own problem or is it
related to whatever is causing the overboost?  IOW,
should I pursue the overboosting before I even worry
about the check emission lite?
  Finally, I have a noticeably cracked hose, it's a
"T" hose which comes off the top rear of the valve
cover.  Could this cause the overboosting and/or the
check emissions lite?  In any case, what is this hose
for?  
  I seached the archs and came up w/lots of hits for
check emissions lite but none that seemed to occur
under my circumstances.  Plus, got side-tracked on
lots of other good info.  So much to learn,
information overload!!

Much thanx,
Keith L.
'89 200tqw

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