Hello List,

I have a 91 Syncro that has been showing a slight build up of black residue
on the tailpipe.  It is not smoking, just a small amount of soot.  Plugs are
chocolate brown and power is about 5 -10% down at low RPM with a bit of a
vibration, normal at high RPM.  Is this a tuning issue or other?  Thank you
for your thoughts.

 

dylan