dont quote me on this but im pretty sure this is correct if not someone will correct me where im wrong

here are the different type of erst ecus


s1 blue red blue no knock sensor
early s2 blue red white no knock sensor
s2 blue red black knock sensor
s2 hearts diamond hash knock sensor

all the ecus bar the hearts diamond hash are 7 psi from the factory but can go to 8-9 before overboost cuts in

hearts diamond hash ecu are 8 psi as std but can go to 10-10.5 psi before overboost cuts in

if u use a knock sensor ecu on a car without a knock sensor within the wiring loom then u will have probs as the ecu wont be recieving a signal from the knock sensor so the ecu thinks there is a problem as there is a break in the circuit

so basicly if u have a car with no knock sensor in the loom then u can use the s1 ecu or the early s2 ecu

if u have a car with the knock sensor wiring in the loom then u can use the s2 blue red black or the hearts diamond hash ecu

as for chips all they basicly do is just remove the boost limit thats it apart from the turbosystems chps as they also do something else but i couldnt tell u what