Originally Posted by foreigneRS
unless your actuator is connected directly to the compressor housing, the actuator will normally 'see' less pressure than the compressor housing (or inlet manifold or wherever you are measuring boost).
it's not a case of the actuator does nothing until you hit x psi and then it opens the wategate to maintain that boost pressure - it's always seeing some boost pressure on it's diaphragm that is pushing against the spring inside it. as soon as that pressure starts to overcome the spring force, the wastegate will start to open slightly.
as your t34 has a larger turbine housing than your t3, it is easier for the exhaust gas to escape, and this will affect the boost level that you get.
but hwen it escapes, the wastegate will close again...so it should still keep the same pressure if set the same.
my question is, how did you keep the actuator set the same when you swapped turbos?????
surely you moved it from one turbo to another, and so one wastegate to another.....that would alter the tension on the wastgate in itself wouldnt it?