Van losing power esp on hills; sometimes jolts in/out of gear; start-up problems

What is your question?

Long running problems with severe loss of power, esp going up hill. We had several cylinders misfiring, so have just replaced all the ignition wires and the coil pack, which we thought would be the answer. Things have improved slightly but we still lose power going uphill once the car has warmed up. Sometimes it feels like it is jolting into gear. Once power is slipping away it is impossible to get many revs. Also, it is erratic when starting up in the morning, sometimes it cuts out a few times first. After replacing the wires and coil pack, we immediately got these codes on our ODBII scanner, for the first time - 17952 (P1544); 16505 (P0121); 00518 (P0121), which are all related to the throttle. We are confused as to why the current symptoms are similar - altho not as severe - as the symptoms we had before replacing the wires and coil pack, and yet we had not had these throttle codes on the scanner before. We are driving the van in Latin America, so it is not easy to get parts, nor to find mechanics who know anything about this model of VW. any tips hugely appreciated. thanks