adamski frst,
i have a small turbo model mate that has just had the 305 upgrade as stated take off the kick plate you will plainly see the chip you will also require an uprated fuel pressure regulator uprated fuel pump and the actuator pressure reset.
they do indeed have an amal valve that is situated on top of the intercooler opinions vary on wether to remove them or not as they do stop you just boosting until it goes bang but a correctly set up bleed valve with restrictors in the pipe to only allow required amount of boost and they can eliminate alot of problems with the valve.
you already have an exhaust i assume it has no cats in it as they have to be removed.
standard t25 runn 9psi and over boost to around 14 psi to allow greater over taking (i think).
hope this helps a bit but if i was you id keep the boost low as you will be probs doing damage already.