Hey just wondering if anyone can help me out with this. I have an 06 Ranger Sport 2wd 3.0 litre. Runs pretty smoothly, I have changed the plugs, air filter, pcv valve. On really cold days. Like -15 Celsius (Canadian) and colder my truck will periodically whistle. It’s not all the time, happens on acceleration but when I let off the gas it stops. Once the truck is up to operating temp and running for a bit there is no whistle. I am thinking it’s a vacuum leak but really have no idea where to start. On a side note this was happening before I changed out the above mentioned parts. The Pcv valve is seated correctly(already checked that). Truck has relatively low Kms for the year. 146000kms (about 91000miles). Has anyone else encountered this? If so were you able to trouble shoot and find the culprit? Thanks

Thanks what should I be looking for ?