Turbo Sounds Different/Loss of Power

[whiplash willy]

I have a stock S13 SR20DET (stock boost stock SMIC) with a 3" DP and Exhaust. The other day driving to work I heard something hit under my car then fall to the ground. It sounded like a large, thin piece of metal. I am not sure if something fell off my car, or I ran over something. Since then, when I hit boost it sounds different, and I don't feel the power I am used to. My AFR #'s are about the same as they have always been (14.3-15 at cruise and 11-13 under boost), but it seems like my boost psi is about 1psi less (around 6-7) then before this happened. The sound of my turbo is different too. Its a much lower pitch sound, and I can sometimes hear the flutter of the compressor. Other then that it drives the same off boost. Ive checked my turbo, manifold, DP, and exhaust and everything is still bolted tight from what I can tell. I can't figure out what the problem is. Any ideas?

[fast_s13]

did you check and make sure you dont have any boost leaks? also pull the inlet off your turbo and check your shaft play and make sure it spins freely