A concealed wall-mounted folding urinal has a main body adapted to be mounted on an internal wail of a bathroom or lavatory in a building such as a dwelling. The metabox container box can also include a box which indicates the relationship between each of the meta boxes stored in the metabox container box. The microscopic hole sensor assembly further includes a microscopic hole plate with a microscopic hole positioned thereon for communicating the front pool and the back pool. A deviation between a target supercharging pressure corresponding to the TCV control duty value and an actual supercharging pressure is calculated each time the TCV control duty value is changed by the predetermined amount.