My 4 speed AT is growling when on the pipe

[littlejoe]

I have a 1991 NSX with shift-able 4 speed AT. It has been very robust going through the gears (Supercharged with headers and Computer for 370hp dyno) but now I am getting a little vibration when going into 3rd or 4th with the gas on. If I let up before pushing into those gears it is fine. Any ideas and how much is a low mileage or rebuilt AT?)

Thanks, Dave