How much is it for a real flow master fot a mustang 2000 gt? What about a hood scooop?

FLow master exhaust has nothing to do with a hood scoop. They vary in price depending on what kind you want to get. Straight pipes with baffles? Curved pipes? 2”, 3” ???? Stainless, ceramic?
I paid around $2500 for mine. It is ceramic with 3” straight pipes.
As for a hood scoop. They are used to help cool and speed the intake up. Hood scoops are not really needed anymore with everything else they have out there. Look up some K&N intake set ups.
Are you looking to just beef up your ride or are you going to race it?

Whoaaaaa…$2500 for a ceramic Flowmaster exhaust? Seriously? What kind of car do you drive?

You should be looking at roughly $500 for a Flowmaster cat-back for your mustang but you don’t have to stick with Flowmaster just because you’ve heard of them. I’m not a Mustang guy myself, but I’ve heard a lot of good things about the Bassani Quiet Thunder. Supposed to be the best sounding and highest performing Mustang exhaust under $1,000.