So this question is more for curiosity than to fix a problem. Already have profec to handle the problem. I've read all kinds of posts of people talking about factory boost between 7-12 and the boost control solenoid and the vacuum hose restriction, etc. I'm trying to figure out what the factory boost control solenoid does and what stock boost really is. Car #1 is sr swap done by myself using a silvia clip and I extended boost control solenoid wires and used it like stock set up but removed stock restrictor hose. Car is full of bolt ons w/ T28 but nothing internal. I have used both stock #62 ecu and Blitz access stage 1 ecu which is supposed to be boost up. Always boosted half a bar max whether BCS was plugged in or not. Car #2 is sr swap done by ? without BCS and gets vacuum from hotpipe, also full of bolt ons and T28 and unknown internals. Always boosted half a bar max. So, with or without the BCS, both cars basically only boosted half a bar. So then factory boost level is half a bar, but what role does the BCS play that the wastegate and stock bypass valve don't do? Seems like a back up to keep it from spiking just in case something fails. Probably just an old school '80s turbo thing. All those old school turbos had all kinds of weird restrictions and controls to keep the car from blowing up. Gotta love it, except when they ran a pipe straight from the turbo exhaust to the throttle body. No intercooler is ghey.