Your loss of power could be anything from a vacuum leak, to your timing has slipped, to a duff spark plug, to a bent valve, to a cam belt that has jumped a tooth. Without having a good look I doubt anyone could do more than hazard a guess.
***DOES YOUR PREVIA HAVE A MAP SENSOR??
If not then its because Modern fuel injected cars either have a MAP (Manifold Absolute Pressure) system or a MAF (Mass Air Flow) system and yours has the latter. This is located at the air intake box where the air filter goes and is identified by the wiring loom that plugs into it. So im guessing that yes, Change your air filter man.
Hope i helped
my toyota previa loses power mainly going up a hill at about 3000 revs and drops to 40 - 50 mph?
Linear Mode
