RPM goes down even on full throtel

[rafiquae]

the RMP goes down after driving for an hour nonstop

this is a very rare thing but i need to fix it before it becomes a major problem

what is causing this

please help me

[saif1404193293]

Gte computer check, my doubts are:

Spark plug not good, HT leads or Ignition coil need change.

Fuel filter or fuel pump need change

Some electrical issue in ECU and its malfunctioning.