2005 Infiniti I30 Service Eng Soon Warning Light in dash

I just bought this car used - and when the check eng light come on and did not go out I took it to the dealer for repair - they said the intake solenoid was clogged and that the oil needed to be changed freq to prevent - after about 2,500 more miles I got the same and took it back to the dealer - this time they flushed the system and replaced both intake solenoids saying it was the same problem - after about 2,000 more miles I got the light again and took it in to a oil change place, had them flush the system and after about a day or so the light went out - another 2,000 miles and the I have the light on again - it does not blink it is just on solid - I checked the gas cap and the air filter and tried holding down the pedal for 10 sec to reset but still on and values do not sound right - do I really need to change oil every 2000 miles to avoid this?