Is a Cat and Muffler Delete legal in the state of PA? i have an 87 Mercury Grand Marquis and i want to know if its legal
removing the cat isn't going to give you much power though. remove the mufflers, and block off the EGR, sure.
probably not, since the gas still only has to go through one muffler, and having so much more area through the exhaust means you lose most of the scavenging effect. if you boosted or cammed the motor, it might benefit from more exhaust area, but otherwise, having it at stock size (or maybe a little bit bigger) is best for performance.