It may seem simple to grab a solenoid and wire it up. But there are a LOT of considerations you have to keep in mind. Not only does the solenoid have to be electrically compatible with the ECU's drivers, but the solenoid has to operate properly under high pressure conditions.
The ECU expects the solenoid to provide around 28-33 Ohms resistance. If you use a solenoid with too little resistance (or draws too much current under any condition), you run the risk of blowing the ECU's internal driver.
The one 3-port solenoid that we've tested to work well without any modification or restrictor setup is made by Ingersoll-Rand. It's Aro model number P251SS-012-D. You can find this solenoid on Grainger's site by searching for that part number or Grainer's part number 6JJ52.
We now have this solenoid available on our website bundled with appropriate 1/8“ NPT nipples to go to standard 3/16” vacuum lines.
The factory boost control solenoid (BCS) does actually work, but it's only a 2-port solenoid. Which means you'll need to wire it up with a restrictor (we've found that a 0.025“ restrictor works well) similar to the stock configuration and you'll need to remove the internal restrictor found in the stock BCS itself.
The one advantage here is that you can plug the solenoid directly into the factory harness without need for cutting and soldering wires into place. You'll just spend some time locating an appropriate restrictor “pill” from somewhere. These are probably readily available, though. Just search for "EVO" boost pills or something similar. It has also been suggested that you can just use some 0.025” welding tips instead.
If wired straight to the ECU, the “typical” GM BCS will blow the 1990-1997 ECU's BCS driver. To prevent damage to our ECUs when running the GM BCS, you have to wire a big series resistor and, possibly, a protection diode across the BCS pins.
Given the effort required and cheap alternatives, we feel this isn't a good choice.
The factory EGR and fuel pressure solenoids are options, but do not seem to work properly much above 25psi. These solenoids either hang open or get locked closed (depending on configuration) under high boost conditions, making them unsuitable for this application.