Keith Garrison

I cut off my muffler, what problems could come with that and what codes could that throw? Also what exhaust system would be best for a 2005 4.0L

m05fastbackGT

As also stated in the thread you submitted in the General Mustang Chat sub-forum. Here's the same response.

Keith Garrison

I've looked or I wouldn't have made a thread

m05fastbackGT

Just to clarify, axle-back mufflers do not affect emissions nor throw off any error codes. On the other hand, if you were to remove the catalytic converters and run straight pipe? you would then have error codes along with a check engine light. As for which exhaust systems are best for a 2005 4.0 are concerned? everyone has a different opinion as to which sounds best. Some like Borla, while others prefer Magnaflow, SLP performance, Pypes performance exhaust, Ford Performance Parts, MBRP and so on. In the end, it all comes down to personal preference. That being said, I would suggest going to YouTube and check out some of the exhaust video's and find out if they provide the type of sound quality and appearance your searching for and go from there. Also websites such as American Muscle, Late Model Restoration, CJ pony parts, stage3motorsports and Summit Racing all carry the manufacturers exhaust systems that are mentioned in stock.