What is wrong with my 96 nissan maxima, it is making weird noises, rattle from the back, whistle from front?

When at 2k rpm or higher, there is an whistling sound coming from under the hood. There are no mods on the car at all, but it sounds almost like i had installed a new cold air intake. It begins when the car is at 1.5K at a very low sound, gets noticable at 2k and gets progressively louder, but only happens when the car is in gear. when i am driving it sounds very odd because i have never installed any mods or anything but it really does sound like a new cold air intake. As well as that problem, when i shift gears, there is a rattling noise from the back, it sounds like a mixture of a rattle and a clicking noise. It usually only ever happens when i switch gears at rpm over 3k. i have no idea what either of the problems are, please help, thank you!
What is wrong with my 96 nissan maxima, it is making weird noises, rattle from the back, whistle from front?
For the whistling, check for a vacuum leak. For the rattle, make sure the exhaust system isn't loose anywhere.