i have a gibson catback on my 1997 expedition 4.6l and am getting ready to swap out the muffler with a flowmaster because the gibson is to quite for my taste. i want an agressive sound and the guy at my muffler shop recommended the 40 series or a sinlgle chamber flowmaster, my question is there any loss of power between the gibson and the flowmasters and is there a power diffrence between the 40 series and the single chamber. i would rather have the louder single chamber but dont want to loose low end but if the loss is minima or nonexistant i will go with the sinlge chamber. p.s. does anyone know if the gibson catback is 2.5 or 3". thanks...

 

If you have the stock cats in place you will have more then enough back-presser with any muffler.You could run it without a muffler if you wanted.

Phil