Almost all breastfeeding moms have one boobie that is a powerhouse and the other is a tad lazy :)
That said, most BABIES prefer one boobie over the other and that tends to set them up to produce different amounts (I say my son likes the vanilla side better than the chocolate)!
Babies are also better at drawing down your milk than a pump. I did find that what helped speed up the slower boobie was getting adjusted at the chiropractor (and I had my son at 5 months adjusted as well). Breastfeeding moms tend to be more misaligned that bottle feeding moms due to the way we hold the baby when we nurse (even when we nurse in bed). Our babies tend to get out of alignment as well.
And just so you know: It is not a bad thing to have one super boob. I know a woman who only HAS one breast due to cancer and she exclusively feeds the chunkiest little girl on that one boob!!! She is now 15 months and 34 lbs!!!!
You can try to trick the slower ta-ta: Nurse your son briefly (like a minute) on the slow side, then switch him to the "super boob" while you pump the slower one. Sometimes just getting the baby to start you off is all it takes to get your milk really flowing.
:)