Hey guys. Looking for a little help. My 2000 Grand Prix GT 3.8L V6 has suddenly started running really rough. It's sounding like an dump truck @ startup and has an exhaust type burning smell. When I accelerate the tach goes to approx. 3000rpm @ just before 20mph. Once it changes out the tach drops back to normal and repeats this process upon the 2nd changeout. After 2nd changeout it accelerates fine but still running really rough. Has a bad shake when first accelerating. I just changed plugs & wires approx. 7 to 9 months ago. I swapped coil packs around and no change. I also disconnected battery and unplugged MAF sensor, let sit, reconnected battery and started. No change. I'm kinda lost @ this point other than thinking catalytic converter, (which I hope it isn't) or somehow all the coil packs are bad. She's always ran excellent, would appreciate any knowledge or help towards this matter. Thanks in advance.