[s-cars] '93 S4 running rich

[PfoHo Masters]

During a recent spirited acceleration in 2nd gear I heard a "pop" and
lost boost.  The hose clamp on the passenger side of the cross-over
pipe was badly rusted, and it had simply let go.  With a new hose
clamp boost was back to normal.

At about the same time, but perhaps unrelated, I have an intermittent
smokey exhaust when the engine is either hot or cold.  Sometimes it
is very heavy and can be seen clearly through the rear view mirror
while driving.  Other times it is barely  noticeable, but never gone.
The engine runs smoothly, no miss-firing or other symptoms.   The
plugs, which are relatively new, look fine, but I replaced them just
the same, with no effect.  Using the check engine blink system no
codes are indicated.

Any suggestions as to whether the apparent rich fuel condition could
be related to the lost boost incident, or where else to look for the
cause?

Many thanks, Jim