Unless the engine check light is on your problem must be service related.
With my clients who come into my network with vehicle as you described I generally ask the following questions;
-when last was the intake,throttle body and injectors properly cleaned.In case of injectors removed and serviced.
-when last were spark plugs changed and if so with what.
-Has the vehicle suffer any overheating or associated trauma.
-How regularly is the oil and filter changed and with what products.
Most times I have found that the average owner demonstrates a loose maintenance regime and does not for instance do a full "baseline" service every 18 to 24 months using proper consumerables.A full service which is designed to baseline the vehicle will normally manifest a 'poppin' in the performance of the vehicle and is quite unmistakeable to the owner.