Correct, but I assume you did it" because it was there"! Emission control gear causes that,ties up with another thread about cleaning emission parts.Do not take off brake to servo pipe as it will cause engine to run very lean,If you have old-fashioned stuff called REDEX (ask your father) then simply pour it into the intake,pause , and rev the nuts off the engine, all the crap on your valves and intake butterfly will go through the engine thoughly pissing off the neighbours but cleaning out the engine.