Recent upgrades or new parts: Iridum spark plugs, fan belts, new mass air flow sensor, PCV valve. The car hesitates when accelerating. However, once it's in the open road it drives ok (not great). I've taken out the K&N filter and placed a normal paper filter in (not much different). The car was driving at cruise control and going uphill it stalled slightly and took itself off of cruise control. My mechanic ran it through the PC (diagnostics) and said that everything is running fine.
My car has 78250 miles.
My car has a manual transmission.
There are a number of things that may cause the car to hesitate when accelerating such as low fuel pressure, a dirty or faulty mass air flow sensor, clogged or dirty fuel injectors, a faulty throttle position sensor or potentially a bad fuel pump. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.