l asked earlier about the dual exhaust system for my 96 grand marquis which you can see at http://cardomain.com/ride/2523030/1 feel free to check it out
i wanna know the good and bad things about adding the dual exhaust especially wether adding it will kill gas mileage

The Cons are increased cost of material, and more things to go wrong. The pros, lower exhaust back pressure, better performance, better looks.

It will not kill gas mileage, you can lose power,if you install he wrong syatem. you need to talk to an exhaust specialist like heddman headers, or even a sales rep at Summit racing. l do not know of any cons, your car will sound better, breathe better, therefore perform better, you may want to consider a cat back system for that application, instead of a true dual exhaust (headers) though.

The only cons that l can think of is the extra cost. Your car should actually see a slight increase in mileage as it will be working less to get that huge car up to speed & up hills. If u see a decrease in mileage, that is usually a side effect we call ''lead foot syndrome.'' This happens when V8 car owners enjoy the sound of their car, & want to hear it more. There is a notch in ur rear bumper for the single exit exhaust, see if u can notch or get someone to notch the other side to match. It would look oh so smooth.

Being a certified mechanic by trade l have come to know that there r plenty of benefits to having a dual exhaust system how ever u can misconceive what ''alot of exhaust'' can do for ur motor. First off a fuel injected powerplant is a ''tuned'' system & requires a certain amount of back preassure from the get go. Given that the ECM will adjust timing & AFR with even the slightest changes dosnt leave everything else u upgrade the engine with way to big parts like the exhaust. to be on the safe side l would go with a catback system but dont go crazy with the diameter of the pipe. Normally doing so will result in a cool ass sounding exhaust with no bottum end hardly at all. l see these youngsters putting these 3'' exhaust on their cars & trucks all the time. Big waste in power where needed. My advice, contact the seller & ask questions. do ur homework. Youll thank yourself in the end. l hope this helps.

The '96 Grand Marquis is not very tuned. You will probably gain some horsepower but might also get a Check Engine Light.

Look into the dual exhaust used on the limited production Mercury Marauder that came out a few years ago.

Cost money if there is nothing with the old exhaust system.
Dual exhaust may save gasoline, but the money spent on dual exhaust, wo not make up for extra gas.