Im no expert but pretty knowledgeable on these, owned two and hve 90% restored my current wagon..Electricl issues first, wiring harness on engine and the electronic throttle..must be okay or you waste your time. Then the fuses need cleaned and changed to copper from the original aluminum which corrode..cause all sorts of gremlins..Then a new upgraded OVP relay which is pretty cheap..start eliminating the trouble codes and ...any cyl head issues/ head gasket or egr system with typical clogging up of the air tube and cyl head ports..