by surge he means don't put your foot in the radiator and then lift suddenly... it can cause the wastegate to make a "chatter" sound causes major pressure differences on each end of the shaft (exh and intake) when it chatters it causes the shaft to twist... think of twisting a crayon. it's pretty tough for what it is; but enough force with snap it and it happens with out warning. i've heard phat shafts are pretty resiliant. if you want to stick with the HX-40 get a boost elbow that controls the wastegate. should level out the boost input to the wastegate actuator
The surge is not the wastegate as non-gated housing turbos can Bark or surge as well. Caused when you reduce the exhaust input to the turbo suddenly and the turbo slows down with high pressure on the compressor side. This pressure starts to back flow through the compressor and causes the "bark" sound. This sudden pressure change stresses the turbine and compressor wheels as well as the shafts and can cause them to break in the HX40. The HX40 has smaller shafts with big wheels and is not a strong turbo, but relatively cheap.
i barked my hx35/40 hybrid more than a dozen times on my truck shifting durring hard fuel, since my truck is a 5 speed the turbo is currently on an auto and does the same thing, they are weeker shafts but i guess i got luckuy