Critical hit for 1000

My motor runs fine, cranks up fine, its just when i idle i can see my rpm gauge go up and down booging up and down until it shuts off. Only way i can keep it running is if i press the gas and keep the rpm's at 1000 when idling. I was told it was the idle al sensor, but i wasnt....replaced it. also the check engine light is on as well. got some codes which are p0174 and p0171. I was told that it means its running to lean. then i was told its probably a sensor. Dont have a mass air flow sensor, so...not sure what else it could be???? im about to critical hit it for 1000 and say screw it, but i have to figure this out. help me

Since you have codes, we'll guess it's > 1996. Don't have a MAF sensor? Did someone steal it?

yeah its a 2000....but the owner before put a K&N air induction thing in ther so there's no mass air flow sensor...but ive had it for close to 2 years ands thats always been there and my car just started giving me problems a couple of months ago. critical hit

Gotcha... The reason I was curious about the MAF is; I had a intermittent p0171 & p0174 that was cured by cleaning the MAF sensor.

Re: K&N, I hear their real hard on the sensors, causing failures from the oil coated element.

You might be better off going over to the Ford Trucks/ SUV's forum here, or LincolnsOnline to get more hits on your questions.