Get a proper Stage 1 chip from someone like Turbosystems, they will do an exchange ECU I imagine. Then get it fitted along with a -31 Actuator and a brass 3-way lockable bleed-valve. Once thats done, have a proper RR tune by someone who knows what they are doing (like us!!) and you should see around 30-35bhp above standard. Not really any nasty stress on the engine at that point providing its in reasonable condition and looked after and it will put a grin on your face!

Worth renewing the fuel pump though if there is no record of it having been done.