I saw a post concerning removing the charcol filters and replacing the stock filter with a K&N or similar high performance filter
does anyone know where I can purchase filter? Also, has anyone used an aftermarket chip and if so is it worth the money? I was also thinking of replacing the exhaust with a true dual system, anyone done this on a 550i?

 

AutoAnything.com for the K&N filter. Should cost you around $40 and they might even ship it for free.

 

The 550 has a true dual system as far as I can tell, it just doesn't look very impressive from the exterior since both mufflers vent out the same side. Did you mean you want to install a quad exhaust?

 

I do agree there are 2 seperate pipes but they terminate into one muffler, which is very quiet, I also have a 01 X5 and the exhaust note is much more aggressive

 

I actually like the way the 550i's exhaust end is setup right now. It's very simple and very stealth/sleeper-like, yet classy. I don't think if converting it to quad exhaust like the ///M5 will yield more power than it's current setup.

 

no, look closer. There are 2 mufflers on a 550. The two exhaust pipes are coming out of separate mufflers right next to each other.

 

And I would also note that almost all of the aftermarket exhausts I have seen are a single muffler, so they are unlikely to improve performance even if they sound more aggressive. You would have to go for one of the better quad options to maintain dual mufflers.

 

If going for aftermarket dual or quad exhaust, one will lose low end torque significantly since it does not have vacuum-controlled flap to inscrease/decrease back pressure.
At low RPM, only left side of exhaust is open, and this creates high back pressure. I believe this increase low end torque
At high RPM, both left and right side of exhaust are open, and the sound is louder and more throaty. This will decrease the torque, but increase hp.

Test it for yourself by tie-up the flap of the right exhaust and keep it open. Go out and test run to see if you can feel low end torque is weaker.

 

Interesting comments and very much appreciated....don't want to loose performance so I'll guess I'll leave it alone...I just want to hear it like I can in my X5.

 

You not only don't lose performance, but you would gain performance if you do up to 6000rpm+ frequently. I don't know 5 to 8hp, maybe. Because you rise up hp at top rpm, you'll lose low end torque w/o increasing engine displacement.
Think about Acura TL, Lexus IS350, G35, and M5, etc, you see that they yield high hp at high rpm, but their peak torque is not even equal to hp number like the case of BMW, and you have to raise up to 4000rpm+ to get the peak torque.
Look at MBZ, they have constant and good low end torque from 2000-4000+rpm, but their 5.0L yield only 302(?) hp.
All this means that you trade hp for torque. So, think of torque and hp on a see-saw for a fix displacement. If you increase hp, you'll lose torque