New supra, computer problem, turbo problem?

[mamory]

I just acquired a 1988 automatic supra turbo. I am fairly new to supra's and very new to and auto turbo. The car is immaculate with 130,000 miles on it. The car runs great, idles great and drives down the road flawlessly. Now the problem...first of all the speedometer does not work and i can hear a gear grind sound behind the speedometer. If there is a quick fix for this?i do not know. Secondly when i accelerate I am getting no power and major hesitation. I can slowly press the pedal down or mash it WOT and the same thing happens. It lags and will not really go above 4000 rpms. I can see the turbo gage working when i accelerate it is going up to about 7 ps and usually stays there as long as i hold the pedal down. The car stutters and feels like it is confused. Shifting differently everytime i press down th pedal. I also noticed while on a neiborhood cruise tongiht the O/D light on the dash started to blink/flash a few times...is this a code?does this have to do with my spedometer?could this maybe all be tied into the acceleration problem?? any advice or help would be greatly appreciated. thanks