Well, there called alignment sleeves for a reason. Its easy to get the intake port openings in the intake misaligned enough with the ports in the head to cause sealing problems with the gasket if you don't use them. Many people have been successful in eliminating them because they were lost or just didn't know better and didn't have any bad results. But as they say "A blind squirrel finds a nut every once in a while". I would use them if I were you, you might just save yourself a headache or two.

We cannot solve our problems today using the same thinking we used when we created them!

Albert Einstein