Cartridge CT16 17201-30030 17201-OL030 Toyota Hiace 2.5 D4D 2KD-FTV

I turned up the boost on my turbocharger and now it’s unstable going up and down. Why is it doing this?

That is called a “BOOST SPIKE”. This can be caused by a bad wastegate design and/or location. It is more common on internal wastegate systems. The port on internal wastegate systems is usually too small or at the wrong angle to maintain a stable boost level. A wastegate port that is too small will not let the exhaust gasses escape fast enough to slow down the turbine wheel.