http://www.200sx.org/index2.html

3.18 What's this about a free boost upgrade?
It's true. You can get a 1-2 psi upgrade by removing the boost restrictor on the top of solenoid valve. It is identified by a white band on the hose which goes from inlet pipe to the solenoid valve. This pipe is at the top of the boost control solenoid. If you don't want to cut the hose, just get a piece of 1/4" fuel hose the same length.

Remember to reconnect all hoses. There is nothing left off or disconnected after this modification. Take the car for a drive and watch your boost gauge. Make sure there is no major increase or decrease in boost level. If there is, stop and recheck your work!

One or two PSI might not sound much, but remember that the export-spec cars run around 10psi (0.7 bar), this is up to twenty percent, or somewhere about 8-10 kilowatts at the rear wheels. On an S15, we saw 20KW at the wheels. Not bad for nothing!