I have an alternate heat riser version... I took off my manifolds and the heat channel on the intake was completely closed from carbon buildup... I guess the good news is that I also was missing the spri g that opens and closes that flap but it took lots of wire brushing, a foot or so of cable in a drill as a drain snake and some sandblasting and pressure washing to get it cleaned out... So it is possible for one position to be blocked 😄
