Well this is my first post, i have been a devoted cadillac owner for 8 years. I started off by owning some very old ones and still have them, recently i bought a 2006 CTS 3.6 6 speed manual for my daily driver, it has 116k miles on it so i got it on the cheaper side. for the last two weeks ive noticed my acceleration is sometimes great and sometimes horrible, its like the torque just disappears, no matter in what gear, when its happening it doesnt matter how much throttle i give it it doesnt go any faster. i have already replaced the plugs with new ac delco as it looks like it was never done. No lights come on when it happens. also sometimes i get slight rough idle. im not sure and i dont have a scanner but could it be a bad coil?