Ok I am buying a Flowmaster exhaust tonight, SI/DO. But I am having a hard time deciding which way to go, 50 series or 40 series. Any input? I have a 03 5.4L

I went to the flowmaster site to listen to the sound but you couldn't really tell because none of the demo's for both of them where from the same vehicle.

 

i put a series 40 si/so with 3 inch pipe on mine and i like it. i think the duals will make it louder than mine but the 50 would sound good too. a friend put one on his expidition and it was nice but a little quieter

 

when i first bought my f150, i had a 50 series on it. i didnt know too much about exhaust, but i went ahead and bought a 40 series. (dual exhaust w/ 3" tips by the way) didnt notice any difference in external sound. i did notice a little more drone which i liked inside the cab. if you buy one, buy one from ebay for $39 brand new. might save ya 60 or 70 bucks. i learned the hard way which i ended up taking off my 40 series about 1000 miles later and now i have dual straight pipes.

 

I've had both as well, both si/so, they same about the same outside, the 40 is louder inside, with more drone.

 

Thanks, I think I will be going with the 40 series off ebay. thanks