Toyota corolla model 2003 showing power loss at times specially on hills why on 2003 Toyota Corolla

it was bought only recently but it was a used one; oil both motor and transmission has been changed recently but when i drive it specially when the driving is on hills or mountainous areas even though i press the accelerator pedal to the last position it would not move beyond 40km/hr but on level roads I tested it and it can move beyond 110km/hr so how could i fix the problem what parts should i get checked by the mechanics or technicians I would appreciate for your cooperation in advance

Asked by for the 2003 Toyota Corolla
2 answers 3 comments
scan test for codes and check fuel pressure
what else should I do and will u help me by sending me the corolla repair and maintenance manual book or tell me here I can get it easily
get a diag and est as you think.have them scan for codes and post so we can adv
WHICH DIAGRAM
get diagnoises from your mech