Ok, so my twin brother owns an 04' mach 1 with about 85k miles. Just basic bolt-ons. The car ran great from 80-85k miles. Well before he left for iraq the car developed a tick, the tick is not from the top of the motor and it is a tick not a knock. The tick sounds like its coming from the bottom of the car, towards the back of the motor and can only be heard when the car hit's between 2-2.1k rpms. This happens if the car is sitting or if it is driving down the road and it is very loud. Any idea's on what it could be? I think the exhaust could be loose on one side but that doesn't explain why it only ticks at 2k rpm's. Could it be the TOB? but it seems to shift smoothly. We had the oil changed once and the morons put slightly heavier oil in the car in the winter and it caused a head tick, put thinner oil in and the head tick went away within an hour of driving so I know it isn't the heads ticking. Any help would be great guys. The noise at 2k rpms can be heard under the car around the car and in the car.

 

My 04 Mach does the same thing, but only when it sits at idle. Ticking from the passenger side and when you stick your head under it gets louder. As soon as you hit the gas or drive you cant here it... I believe its an exhaust leak.
Here is my car: dont mind my brother lol.