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My $0.02, run some dry patches or a bore snake through the barrel a few times and then fire off a couple (10-20) pellets inside your garage into an appropriate trap. Even a cheap Rubbermaid trashcan filled with old rags/torn up cardboard can be sufficient for direct shots. I've done this and never had a problem with sharp supersonic cracks disturbing my neighbors. Also, stick to heavier pellets (JSB 18.13s or better yet Gamo TS-22s) for your first few shooting sessions. The gun will still be breaking in so tack-driver accuracy wouldn't be my first concern, and the heavier pellets reduce the chance of going supersonic even with dieseling.
 
I thought gas piston guns don't do it? I've had my springer do this after I upgraded the piston and spring and had to burn off the excess (I put too much) lube. It was really loud sounded almost like a 22lr and made me instantly put it away lest the cops come. If I had a big yard it wouldn't be a problem but I live in a city with neighbors all around. 

I shot 10 or so shots with a big blanket over to muffle the sound and it's good now, but every now and then I get a smoky shot. With just a new gun dieseling I wouldn't worry about it.