I have a few questions. To start I have a 2004 GT. Is it okay to just take off your mufflers and run a straight pipe? If so does it add any horsepower or increase gas mileage? Also my friend has the same vehicle and he removed the plastic casing around his air filter and left the filter exposed. He said he gets more power and better mileage. Can this harm the car in anyway? Like something getting in the filter? Thanks a lot.

 

You can take the mufflers off and run straight pipe. That is basically what the SLP Loudmouths are. Will not add much if any HP, but will sound bitchin.

 

You might get more help if you post in the other 4.6 section, this is for 05-07 mustangs....I'm not bein a jerk by saying that either so please don't take it that way....Just tryin to help a newbie out

 

Glad you said it not me.