my 740 shudders a little while in park and a little more while in drive and stopped at a redlight. i recently replaced the tranny mount and center support ring which cured some nasty vibrations during acceleration. am i correct to assume that my engine mounts could be bad? what else could it be?

and a completely separate issue...sometimes when i start my car up my gas tank reads empty even though it's not. usually the next time i start it up the problem is gone.