Special K,
I am no expert on this stuff, but, 78 sounds a little on the lean side to me.
It may take some time for someone with more knowledge than I have to give you advise, so...
You may want to send a PM to HotCrusader, Dennis Moore or Infomaniac just for starters.
There are many people on the forum that can give you more detailed info for your set up than I can.
Good luck.