Turbo Boost Controllers
Covers:
The first generation Probe GT has a maximum boost level of 7.3 psi, with a brief peak of 9.3 psi at 3000 rpm. The best way to control the boost levels is to use aftermarket boost controllers. These allow accurate boost adjustments without over boosting.
Home made boost controllers are easy and cheap ways of increasing the boost and are the best 'horsepower-per-dollar' upgrade you can get. Basically they involve either forcing the boost solenoid open or tricking the actuator into believing there's less boost then there is. This increases horsepower without spending much money.
There are three different types of boost controllers that you can do yourself...
Solenoid Actuated Boost Controller
Notice Before Proceeding...
Do not attempt to increase the boost on an engine with possible problems, such as reoccurring engine code errors. This will only increase the possibility of engine failure. Also be aware that increased engine wear and stress will most likely occur under considerably high boost levels as well as the possibility of engine detonation.
I highly recommended that you use a boost pressure gauge to accurately measure and adjust the boost pressure. Even a temporary one can be connected to the intake manifold to get improved accuracy on the boost settings.
The first generation Probe GT has a boost limiter set in the ECU for 12psi. When this limit is reached, a tone will sound in the passenger compartment and the engine will briefly cut out. Although this is not harmful to the engine, do not use this limit as a setting point (for example, keep increasing the boost until you reach the limit, then decreasing the boost slightly). The above three methods of adjusting the turbo's boost is not necessarily an accurate adjustment and occasional overboosting may occur, causing you to hit the boost limit. For Most applications, you shouldn't need more then 9-10psi of boost for reliable performance. Anything more then that, I recommend purchasing an electronic boost controller.