I wouldn't remove the inlet manifold until it causes a real problem... a build up of soot isn't really a significant issue. Problems with the IMRC/swirl valve are often because of the EVR actuator, so do check that this is working OK (no vac leaks & filter OK), It wouldn't hurt to clean up the EGR valve as well (which will also have an EVR actuator, if your Accord is a facelift model).
So one member adds a cleaner and reports less smoke, while another adds a cleaner and reports more smoke. I'm not sure what to make of that!