Originally Posted by
SD Crossfire
I don't recommend the K&N Drop-In filters, they don't fit in the stock airboxes very well, which could allow unfilter air to bypass them.
If you want aftermarket performance air filters, go with an complete air intake.
These sold from Needswings seems to be popular on this forum:
https://www.needswings.com/intake-xf
As for exhaust, I didn't go with a catback exhaust, but instead just changing out the muffler for a better sound. I'm going with Flowmaster Super 44 (2.25" in with dual 2.25" out) and having my muffler shop weld it in place. About $250 including the price of the muffler. You won't see much in the way of performance gains, mostly sound.
Here is the catback Magnaflow system sold on Needswings as well:
https://www.needswings.com/magnaflow...exhaust-system
Not sure I agree with the feedback above about the fitment of the K&N filter elements in the stock air box. I ran these for several years & didn't see this as an issue. I have since changed to just getting the standard air filter design from a reputable supplier & changing them out every couple of years. I don't believe the K&N offers that much of a performance improvement. I will agree that if you want to improve the "breathing" of a Crossfire, you need to consider a wholesale changeout of the inlet air system (just like
SD Crossfire stated above). And upgrading to the larger throttle-body will probably net you the most improvement. This conversion can be bought from
Needswings.com and the Forum has documentation on how to implement this upgrade.