"boost solenoid" ??? explain

[cademfjohnson]

so i keep seeing things around the net mentioning "stock boost solenoids" on rb engines. im newb to these things for sure, but i didnt notice any solenoid in line to my wastegate actuator on my rb20, so im assuming r32 gtst's dont have them.

what i gather is that whatever engines come with this, have electronically adjustable boost level from factory??? someone lay this out for me

[Darius]

RB25's came with a boost solenoid that stepped the boost up from 5psi to 7psi as rpm increased. Everybody takes them out when they get a decent boost controller. I don't think the RB20 had one.

[l0nestar]

Boost Solenoid from a 25:

[cademfjohnson]

thanks for the pic. makes sense