ecu advice
 

i have a 96 wrx with a 6s ecu in it, are there any other factory ecu's i can use that will make an improvement in power ?

If your car is a WRX, the 6S is not the standard ECU in the first place. The 6S is from the 97 STi models, which should have a higher boost target etc.

Slightly more worryingly, the 6S ecu will also have the higher rev limit of the STi. Best to be a little careful not to clang it off the rev limiter too often (by "too often", I mean "ever").

As a rule, using a different ECU carries some risk, as the maps inside may be set up for different sensors, components (turbo, engine internals, cams and valvetrain etc). I think in your case, the sensor pack between the two cars is common, so you shouldn't run into too many problems.

running a genericly mapped aftermarket chip on a scoob is asking for an engine to go bang im afraid.

while chipping isn't a problem the chip needs mapping for the car to make sure the fueling etc is correct

what ecu should i have ?

Your car should have been originally fitted with a 1S ecu.

Saw your other thread though, if you have the engine (particularly the valve train) and other bits from the STi (e.g. intercooler, not sure if turbos were different between 97 WRX/STi) then the 6S would be the "right" ecu to have.