Quick One
 

I was thinking about putting on a whole new exhaust on my 1989 Mustang Lx 5.0 I was wondering what would be a good setup. 3" tubing, flowmaster 40 series, and then 3.5" tips. car already has headers on it, but they look old and rusted so i may replace. Any links i can look at would be appreciated. Thanks

http://www.themustangshop.ca/catalog/300611

they have good prices.
check their sight. or call matt.

i think some might say 3" is too big.

3" is too big, you will lose power on a stock or near stock car. 2.5" is the biggest I'd go unless you're pushing over 400 hp. IMO Flows sound like crap and they actually restrict flow when compared to Borla, Magnaflow or Bassani, but if you like 'em, it's your call, just giving my opinion.

go with 2.5" into a pair of magnaflows and 3.5" tips that start right after the axle they look sooo good and the magnaflows are by far my favorite mufflers on a 5.0 check out the mustang shop they have the magnaflow cat back kit i believe if not go to steeda.ca

well go and check mustang shop you will find some thing better for you.
2.5 with magnaflow kit is much better.

all I know is that going from 60mm piping to 3" gave me about 20whp at 13lbs of boost.

If its too large it can hinder performance by reducing the scavenging capability.

that is really gud