What 5.7 motor did you use as a replacement? Often the vacuum signal will cause the 'rough/ uneven idle'. Please list the EXACT changes you have made. I am currently working on a "dial your fuel curve" system for Mercury (GM) EFI's. If the distributor is not ECM controled, it will 'seek' a level idle. If the distributor is ECM controled, it will 'seek the best mean idle'. ECM's that control the distibutor often drop the timing to -4 or -7 degrees. This is being done to prevent reversion (water into cyls) and to create a "hot/ rich" smog legal idle. The other area of 'rough idle' may be caused by too large of replacement injectors. Let me know.