P0068 Manifold Pressure / Throttle Position Correlation
Vacuum leaks has to be check for this condition, any vacuum leaks will affect the operation of the MAP sensor.
This is the MAP sensor here, vacuum leak will affect the operation of the MAP sensor, or restriction of the air induction system and this inculdes the timing belt
The TPS sensor if the TPS connection properly functioning P0068 can result.
Main causes for P0068 are vacuum leaks, this vacuum hose was disconnected to perform a tune up which required the removal of the intake manifold, the owner did not replace the vacuum hose and as a result P0068 was set. which resulted in rough idle and occasional stallling.