Simonz,

hi, what do these actually do apart from turn your boost up n down?....in other words, if i buy one of these for 20 quid,fit it to my 94 wrx with limited mods , could i release more power? thanks

jonesting

i dont think its as simple as that mate,i expect you need some kind of mapping to set the boost in the first place

briforbes

You can increase the boost, and the factory ecu will be able to add extra fuel and compensate to a degree. It's a very crude method, however, and you would be better getting a z4 ecu or some form of correctly mapped "chip" for your ecu.

If you can stretch to it, a custom mappable ecu such as the Apexi would be most beneficial, albeit at a price. For limited mods on an early car, a Z4 ECU is a worthwhile upgrade - more boost, with safe fuelling and ignition maps on UK fuel.