pro5.0stang

i currently have two exhausts for my 89 gt....mac equal length headers, offroadhpipe, no muffs. and i put on the mac pro dumps once and a while. what i want to do is run the mufflers and weld in exhaust cut outs in the h-pipe for when i want it loud. but still have the macs on and just cap off the cut outs when i want the tone.
what will give me more power?
thanks