[RedRocket321]

Just bought a 1997 Geo Metro 3 Cyl, 5 spd, 128,000. The muffler needs replacing. The question that I am posting is should I go with a stock muffler (autozone) or go with a muffler from (flomaster, cherryboom,etc). I realy do not care what tone comes out of the exhaust but would prefer more of a rumble instead of the whine I am getting now if possible. I can live with whatever sound as long as the mpg is there.
I have read that the stock mufflers give too much back pressure and hurt fuel economy and that the performance mufflers reduce backpressure and help to increase mpg. Could I get some suggestions on what type of muffler and possibly model numbers so I could do the right thing for the Red Rocket.