Exhaust cut-outs serve a purpose for vehicles driven on the track, but on a street driven vehicle it's useless unless your trying to attract attention, which will usually be the wrong kind.
Most modern internal combustion engines require some backpressure in the exhaust (actually they require scavenging of the cylinders during the exhaust stroke which is a product of backpressure). By using an exhaust cut-out your reducing the backpressure thus reducing the engines scavenging abillity and making it less efficient (horsepower and mpg). The cylinder will retain some of the burnt gasses and not get a full clean fill on the intake stroke. At high rpms the engine managing system will only allow the engine to go to a set max rpm, so you'll gain very little if nothing there.
Yes race vehicles use open exhausts, ever seen one take off at anything less than warp speed and max RPM's? They dont, without backpressure they have verry little low end tourque. The engines are built to run max rpms most of their short lives, at these rpms they dont require as much exhaust scavenging to clean the burnt gasses out of the cylinders because of the high flow it's forced out.
Are modern exhaust systems perfect then? No they can be made better with a combination of steel tube headers, mandrel bent pipes, free flowing cat convertors, and free flow mufflers. The combination has to be just right, all these items on one vehicle may actually slow it down. Lots of factors have to be taken into account, axle ratio, rear wheel horsepower, and even the vehicle engine sensors have a role in things.
So unless you just want to make your truck obnoxiously loud to annoy people you should probably look at other methods to achieve more top end. Depending on where you mount the cut-out this method may cause more problems than it's worth.