First I got a check engine light code p0174. I hear a whistling noise coming from the back of my engine while the car is running. I can not find out where that noise is from. I did read the post about this code on top, but before I buy anything I want to make sure that that is my problem. Anyone know what it could be?

I'm not sure what that code means with out looking it up in my manual, but could the whistling be coming from the donut gasket where the exhaust bolts up to the exhaust manifold? I have a similar noise and a noticable exhaust smell on start up and learned that the exhaust on my car has sifted and the exhaust is leaking around the donut gasket. I've been told I need to eventually replace my exhaust, but $1000 is currently not available. Hope this helps.

Read through the attached link for info on the code you getting.

http://www.aa1car.com/library/ford_lean_codes.htm

P0174 is a lean code.

Whistling could be a vaccuum leak

If you told us what year your car was and what engine it has we could probably tell you some year/engine specific problems