This is my exhaust system that I put on my old 91. Mine was an RS 305, so your 350 would have more of a growl than mine had. With that said though, mine was extremely quiet while cruising the open road, and had a nice sound (still not annoyingly loud) when the right foot went down.

 

You have a dual muffler. A true dual is individual piping from the headers to the rear of the car. Basicallyone piping for each side of your motor. Your headers collect together into one pipe untill it get to the muffler

 

And this where I get confused at, the flowmaster website only shows one side as inlet and the other as outlet. theres not one where it has a inlet and outlet on the same side. so does it not matter bout in or outlets and just bout the size?

 

I'll check to see if I can find one for you. They should have dual.

 

depends on which flowmaster model you choose as to whether its a single or dual. if yo buy a flowmaster, repaint it after its been on the car for a while, they tend to rot out at the welds. also, what sort of sound are you looking for? extremely loud, raspy and rumbly, or rich and mellow? theres a lot of choices out there. i put a dynomax 4th gen exhaust on my car (no audio clips yet), its very similar to the slp but has some flaws to it. about 80% of the exhaust goes out the driver side tail pipe, so that one is constantly black. also gets some deep resonance and rasp at 1600 and 2200-2500, but it is ungodly loud and i love it

 

The Flowmaster 10 series I have on the mamba are ridiculous combined with the longtubes. Mine are dumped at the rear axle and its LOUD! If youre cruising over about 55mph it mellows out a little. Below that its pretty rumbly in the car depending on how much gas you give it. At WOT, i cant really hear my radio...

 

I am building my own dual exhaust on my 83 Camaro that I put a big block in. The reason the muffler shop will not do a dual exhaust for our cars is time and materials. I am making my own fittings, 90s 45s and 22 1/2s. Plus I am making my own oval pipe to deal with clearance.