run a strap to the ground under the car!!! worked in teh olden days... maybe go to the manufacturers site and look up their instruction manuals
http://forums.nasioc.com/forums/showthread.php?t=674153&highlight=grounding+mod Instructions, pics, updates and debate.
I don't know about the newer cars, if they are the same or not, but the factory air box had nice bolting points directly on the frame rail. Those are the kinds of things I look for in a grounding point.
I put two on the intake mani, where the stock grounding straps go, one on either frame rail near the fenders.(the ones piddster is talking about), one under the intercooler, next to the transmission mount, then one on each strut tower. That makes seven mount points.