Ok. That's an important piece of information. You're right, its probably not the sensor's. I would say based on that, go back and make sure everything you installed is torqued down correctly. It sounds like a major vaccuum leak to me now.
The other thing to look at would be the C&L Maf sensor. I've heard some people have had issues with them. I can't speak personnally, I still have the stock MAF.