Fuel fumes after Crawford plenum installed.

I've noticed that since I installed the Crawford plenum, I get a strong odor of exhaust fumes, almost as if it was too rich. Does anyone else have this problem? Do I have to torque down the plenum to a certain point? I tightened it pretty hard w/o breaking anything. I usually smell this when sitting and idling at a light or stop. Never when I drive. Let me know! Thanks!