My 02 R53 is way down on power. It has a very bad hesitation also. It does it accelerating and just cursing. What I have done. First before anyone says it, yes my Walmart battery is good! My coil pack and plug wires are only a year or maybe two old. A few days ago I changed the belt, tensioner, idler pulley, plugs and fuel filter. About 2 or 3 years ago I changed the SC oil. When I did the belt this time I turned the SC by hand and it was tight and smooth, no noise. I also changed the crank seal and the oil leak I thought was the timing chain cove turned out to be the cam position sensor. With the AC on the compressor makes a very very loud roaring as loud or louder then the SC at full tilt. So I know I need a new compressor. I have one sitting in my garage. I have had it about 5 years. I need to check and see if its still sealed good before I buy another one. I thought maybe that was the problem but it runs the same with the AC off. So All I can think of now is maybe a bad CAT. I meant to check it when I had it in the air but forgot. I have a new exhaust so I know that is not it. The cat is the original and it has an OBX header.......Yes OBX. If its the CAT I don't know if I want to get a high flow CAT or get a stock exhaust manifold and cat used from Allmag and remove the OBX header. I have almost 160k on the clock. I told my wife the best fix would be to send the motor to RMW, she rolled her eyes and walked away......not sure what that means. So any ideas?