Originally Posted by Young Performance

It really depends. NA engines don't usually have much variance. They are usually within .5 or so. SC engines can get pretty bad, especially if the blower is spinning really slow. Whipple's can be really bad if they spin slowly. It's really only a problem when the engine is in vacuum. Once the get out of vacuum and into boost, they will usually straighten out. I have seen some engines with Whipples that had almost 4 points from one bank to the other. The only way to fix it is to spin the blower faster. Once we went to DIS, it helped a bunch, but it certainly didn't fix it.

Generally, NA engines will be close. I don't think I have ever seen one with more than 1 point difference. SC engines can be bad and certainly need to be checked.
Eddie