OK well i have 2002 Honda civic coupe with around 95k on the odometer , (d17 headers , exhaust , k&n air filter) well this car has many problems . But the main problem which i have not diagnosed yet is these crazy vibrations/shaking i have bin getting lately when im in nuetreal. When i turn on the ac it shakes even more . the air filter makes a crazy whistling noise when i turn on the ac . (the car has a broken rack n pinion if that helps anything ) . But when i turn on the car its really loud and it shakes like crazy for about a minute and then the loudness goes away but it still shakes . i looked under the car and i saw that the exhaust was shaking around the middle of the car . The air filter and engine also shake . i have also noticed that the mpg and the power of the car have also decreased . any advice ? thanks

 

The engine vibrations could be coming from worn engine mounts. I would inspect them.

As for your rougher idle, you could have a clogged Idle Air Control Valve (IACV), which would require you to remove the throttle body to clean.

Then, for your poor performance, you'll want to look at several things. The spark plugs are a good place to start.

 

Sounds like the engine mounts to me.