1999 Chevy Camaro Misfires

Since I got this car it has stumbled some times not very often under heavy acceleration. But not enough for me to think much of it. But a couple of weeks ago when i got under the car i found a spark plug wire had the insulation ripped off exposing the metal wires. So i had to temporary fix it with a wire that was laying around in the garage. it barely fit the car. I drove with it for for 2 weeks but a couple days after i did that it started to miss really bad accelerating very bad stumbling even at high rpms it sputters. But its not thowing check engine codes. I replaced the spark plugs and wires very carefully torgued them down to the correct amount. I made sure i didnt cross the wires up. It doesnt do it idleing and since i replaced the plugs it has gotten worse and does it somewhat with no load while revving engine.