I recently added a port and polished head with titanium valves on my sohc civic. Ever since the car has run just fine, a little valve clatter even though the specs are correct, but a considerable amount of soot is accumulating in the rear of my car, unlike before. The only thing I can think of is that it is running fairly rich. What easy steps could I go ahead and do to even out that ratio? Also, what cam do any of you out there recommend for the sohc?? Thanks again.