every turbo bolted without blow-off and knocking senzor may blow your engine There is certain set of situations where you have unwanted boost and/or too much air in mixture, thus getting knocks...
Btw blowoff under 14.7 psi will not be best working thing, I tested one and spring had like 3 psi tolerance on 14.7 psi (thus going even to 17 psi) And it wasn't cheap one. GT15 won't go over 13 psi but it valve may get open on 6-7 psi i/o 9 already... sucking feature.

But skilled technician can do adjustments, put in precise valve and get rid of knocking by chip adjustment and it's ok.
I always wondered which chip Van Aaken used to make their turbo working. I can live with idea of MS2 piggibacked and working with stock ECU, so "chip" must be secondary ECU as well. And I bet programmable one.