Stock turbo's will definitly surge with performance enhancements done.
Some play in the wheel is normal, the shaft rides on a coat of oil that is obviously not there when the truck is off, once you start the truck and oil fills the gallery the play is gone unless the turbo is failing which will be indicated though a loss of boost, if there is visible scoring marks on the inside of the housing that is an indication that there is too much play in the wheel but like I said, some play is normal.
Off throttle surge is pretty typical on an OEM turbo and will eventually destroy the turbo, a good designed turbo should not surge. A Low Stall Convertor can usually help out here as the transition into lock up is smoother with less RPM drop, this will also be easier on the lock up clutches and put more power to rear wheels.
It is also common to have the turbo surge when the vehicle goes into lock up if the RPM drop is more than 300RPM when it locks up.
A BD Turbo Guard (Blow Off Valve) will eliminate the surge but ultimately a Super B Turbo is the fix, no surge, lower EGT's and the largest efficiency range in the industry from a single charger.
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