My 03 TJ has had a loud engine whistle for some time now but it only occurs when cold outside most of the time. It wont start until the engine is running for about 5 to 10 mins. It will squeal until i press down on the gas and start again when i let my foot off. It gets progressively louder until eventually it will stop. Ive checked all pulleys and the belt tension, even replaced throttle body gaskets and cleaned the throttle body. Only thing i can think of is a possible air leak somewhere. If anyone else has had this problem it would be a big help to try to fix this. Doesnt effect how the engine performs it is just annoying and can be very loud.