Well, let me put a few thing’s to bed for you, First off, true duals from the stock exhaust manifold’s back will afford some more speed not torque, so long as you replace the stock cat’s with some high flow performance cat’s that are widely available and cheap, Secondly let’s not forget that unless you have a carbureted engine which you do not, you will need a custom tune and probably an unlocked pcm to run the tune. You are confusing the benefits of intake, head, carb, exhaust, non pcm on non catalytic vehicle’s performance changes. Today’s changes involving torque, horsepower yada, yada, yada, start with a tune, a better CAI and some simple exhaust mods, nothing else is needed to get them to run great and stay within legal emissions and now idiot light’s winking at you from the dash. A CAI, a set of long tube/shorty’s, high flow cat’s on a true dual without mufflers can cause a significant loss in back pressure ie: loss in performance if no custom tune/engine work is done. Not to mention it’ll dissipate engine heat causing the exhaust to prematurely rot out Andy won’t operate a nominal temperature during the winter months and that can lead to other issues down the road.
Muscle cars run great for about 65,000-70,000 miles (trust me I owned several big blocks) we also did to them what you think you want to do to yours. Today’s vehicle’s run twice as long get better mileage (some times) and do with with the a/c on. Do a simple exhaust from the cat back put on a CAI change to a better set of plugs, and plop in a pedal commander you’ll be statisfied.