Hi I purchased a 2003 Dodge Dakota Quad Cab 3.9L, 4x4 here in Calgary, Ab, Canada last December. Every time the temperature gets low (0c and lower) I hear a high pitched whistle coming from the engine. This is definately an air flow type whistle (not a bearing noise or squeak). The pitch varies with RPMs and comes on under light/steady load. The pitch varies by feathering the accelerator and can be stopped by coming off the gas or depressing the gas, but eventually comes back. Whistle starts at about 50k and continues right up to 110/120 kph. Very annoying and frustrating. I have looked for obvious vacuum leaks, breaks in lines etc. Only occurs in cold weather. Very hard to replicate on the driveway. Never heard it all summer, but now we are into cold ambient temps and the whistle is back. Any suggestions??