Hi everyone. I recently bought a 2003 Nissan Xterra SE 4WD. It has all options like black leather interior and RF stereo, etc... Full disclosure I've only driven this vehicle once for about 15 minutes. I used to have a 2000 Xterra and I thought it was peppy enough but people in here say the engine is boring. The 03 I just bought seems to be about the same speed at best. It has a bad exhaust and I'm not sure how bad exactly. It may just need a muffler or it may need more. Its sounds to me like there is a knocking noise as if the exhaust is leaking toward the front as well. I made sure it is not the engine that is knocking. Anyways I brought it back to the lot and it's parked there right now. I was going to bring it home today but I got too busy and the weather was awful. At the end of my test drive I was about out of gas so I stopped and put 2 gallons of 87 octane in it. While at the gas station I thought it seemed taller than my older Xterra. Anyways, I noticed the factory wheels on the 03 Xterra didn't look like my rims. I went back to the lot and took a pic of my rims. I also didn't recognize the engine. I just looked different, but it has been awhile since I've seen the Xterra engine. Anyways, I realized that my rims are different because they are the SUPERCHARGED 17" factory Nissan rims. This might explain why the engine looked a bit different. I'm not 100% sure, but I "think" I have the supercharged version. What doesn't make sense is that when I did get on it, and I never got on it 100%, but I did accelerate from like 20 to 40, but I heard no supercharger. But keep in mind, the exhaust is kind of loud. It's not terribly loud, but it is loud enough. When I did get back to the lot, I looked underneath it and it looks to me to have a HUGE muffler on it. So anyways, I've been watching YouTube Xterra exhaust videos. I've seen videos with a Flowmaster 44 and a Flowmaster 50 muffler and I want to go that route. But on one video, a guy is driving towards the camera and going past the camera. You can hear his supercharger make the supercharger "whining" noise. I never heard this in the Xterra I bought. I read that if you don't use premium fuel, a knock sensor can turn on, and at the same time, the car's performance will be retarded and it will perform like a vehicle with no supercharger. Maybe the little knocking that I'm getting in the front of the exhaust is actually a knock sensor. I plan to use premium gas. Maybe the supercharged Xterra on YouTube was modded and therefore louder? If I go to the lot on Monday and pop the hood and it isn't supercharged, then I know it just has supercharged rims for some reason. But if it is supercharged, could the supercharger be defective? I guess I'm trying to ask.....how do you test a supercharger? Maybe I can't hear the whine inside the vehicle with an exhaust leak? Maybe the supercharger isn't supposed to be whiny sounding without being modded? Or maybe the supercharger isn't working because it POSSIBLY was ran on 87 octane gas. I know about Turbo cars, but I've NEVER had a supercharged vehicle before. I will know more on Monday and I also plan to take my Xterra to the exhaust shop. I've heard the Flowmaster 44 and the Flowmaster 50 muffler. I have no idea if the cats were removed or not. Both of them sounded good. The Flowmaster 50 was shot with a crappy camera and had crappy audio but I could still tell that I think the Flowmaster 50 sounded better. Is there a certain Flowmaster 50 that I can order on eBay? I don't know what exact one to get. So I need to know how to test a supercharger, or maybe wake it up with a fresh tank of 93 octane gas? And I need to know what exact muffler to get and if deleting the cats will help or hurt the Xterra. I used to drag race Mustang 5.0's MANY years ago. They all had 4 cats on them and the first thing I modded was installing an off-road H Pipe and getting rid of all 4 cats. But now times are more complicated. You start removing cats on a newer car and that could cause all kinds of issues. So will it cause the Xterra issues? I haven't modded an exhaust in 20 years! Thanks everyone!