its still the same engine but with the 'TDI' turbo and pump on (i think !)

will be around 90 bhp , maybe just under but with a IC fitted will def be 90 in standard form then the same as mentioned before with the tweaking the pump

fitting a T3 is possible but wont give you any more power in theory as a diesel runs with an excess of air anyway , its the fuel that gives power , the turbo is basicaly an emmisions controller to keep smoke down

in theory if you fitted something like a T3 and run it at say 20-25 psi with the fuel regualtor wound completly out then you could get around 130 bhp with little smoke BUT the head gasket would soon start to blow , the IC elbow with split and so on as they arent made to run that sort of pressure and volumes of air (plus fuel economy would be crap) , i have a bleed valve on my standard turbo for when its due a MOT , i wind it out completly for the test to dilute the emmisions then put it back after but even this pressurises the header tank

your original gearbox will fit straight on if you use your flywheel and clutch too , if the box you have been given is from a RS turbo then it should have a LSD fitted and is the better box , this will also bolt staright up and driveshafts also fit no probs