Thanks for the compliments on guia, although the idea was not mine, and the GM does not visit the boards.
I agree that +15 to Intuit Direction is very high. The GM wanted a situation where the Pela were flawless guides in a situation where no one else could find their way. While this seems a bit excessive, the character has ventured far from the Wastes and now rarely uses Intuit Direction anyway. Also, the GM has hinted that the withdrawal from guia will be a very big problem, thereby balancing the bonuses it grants.
To put the situation in context, our party had adventured far from home, across the Pelagic Wastes. They had met and hired a guide, who of course smoked guia. Soon after, my character was killed and eaten by a bear. We have very little access to raising dead methods (used one time in 3 years of play), so I was left to make up a new character. I told the GM that I wanted a dwarf who had been trained as a guide by the Pela, and I think this forced him to flesh out the mechanics of the herb.
seasong is correct, the +1/-1 is to the skill rolls, I supose it is a circumstance bonus/penalty. So no effect on actual INT and WIS scores.
alsih20, I think +2/-2 is more workable as well, but am fine with what it as is. Basically just flavor, but fun.