I have a LS V8 with 63K, had a slight misfire at 50 mph... would come and go not consistent. Now from 20-70mph its a constant miss when under acceleration. I first changed the fuel filter... got better. Now its horrible. Bought a new ignition coil (had one that has a cracked) replaced it... no change so I started swapping them out with the extra one I have. Swapped all 8 with the new one and no change. It idles a little rough after putting in to gear. The previous owner had, under warranty, valve cover gaskets replaced, and 4 coils... also the computer re programed. Spoke with the local dealer and he says it is the transmission. I believe it has to be ignition or fuel related. The ck engine light does not come on.... can they check for a code. Does anyone have any suggestions?