Car has 46K miles
Oil, Power Steering Belt, spark plugs all done recently.
Cat Back Exhaust
Just replaced stock air filter with a K&N filter element.
Other than the above listed, the only other things done to the car was an install of a utec with a stage 1 map and parameters (from their site). This issue occurs regardless if the utec is in the car or not. Seems to have happened around the time the air filter was replaced and the utec was installed for the first time.
Right now the utec is out of the car but it sputters seemingly after it starts to make boost and anywhere from 60 to 100 percent open throttle. No cel flashing or other obvious warnings.
I am thinking it could be the 02 sensor? I am going to be getting a wide band to tune the utec, but until then I am leaving the stock ecu in charge.
Any ideas or suggestions?
Thanks in advanced,