When i bought my wrx it had a Dump valve, turbo gauge and rock hard suspension aswell as a huge exhaust, i want to mod even further but want to do some investigation as to what is already been done. I am especially interested in the ecu but other areas of info would be much appreciated

If the car only boosts to around 10 psi the ecu is prob std.
If considerably more, check under the bonnet for a bleed valve
on the boost lines. If theres 1 present probability is its a Dawse valve or the cars superchipped. The only way to determine the later is lift the carpet on the passanger side footwell.
The ECU is in there, if a S/chip is fitted its a small black box hooked into the ecu loom. To check the ecu itself unless its badged it may be necessary to remove the ecu.

Check all the above 1st b4 pullin the ecu out ;)

Pete