Exhaust and blower

have a read at this. they don't place much emphasis on exhaust for power.
http://www.kennebell.net/techinfo/ford-techinfo/46gtTechTips.pdf

should proably just pick an exhaust you like.

go to mustangexhaust.com and listen. I like borla, magnaflow, bassani. Alwasy pick a loud catback if your keeping the cats. pick more of a normal one if you ditch them unless you really like a loud car.

off road pipe
borla turbo
magnaflow
bassani quiet thunder

catted
magnapack
borla stinger
bassani race

this is just my opinion of corse.
 
I had the magnaflow catted x and catback on my 03 cobra and it sounded like a boat at idle. I wanted the old school sound and found it with the mac catted h and magnaflow catback, I also put on long tubes, but like people have said above, KB research shows no gain with lt's and only 8-12 hp for exhaust !!!