the other day in the shop i saw a duratech auto matic with a major clunking problem and the driver said that the car would handle oddly when accelerating.. we found that the right side cv shaft was not secured. what i mean is thers a bracket holding the carrier bearing(is that what its called) in the middle of the shaft that was just flopping around..is this secured to the block? your problem is definetly motor mounts but this problem gave some of the same symtoms that you describe..

96 zetec gl.dynomax exhaust(self bent) KKM intake..Bridgestone Potenza RE-910's...other mods also
87' Ford Thunderbird..Now my daily driver ( the wife uses the contour mostly) true dual exhaust with the super mystery mod.(hey there not even there!) tinted windows and stereo upgrade. the $200 car is starting to be a great car