Wondering if they hurt the turbos due to backpressure or for other reasons at all.
Also what's the difference between the generic mufflers on ebay and the brand named axles backs or mufflers?

 

I don't think a silencer is going to hurt a turbo anymore than a normally more restrictive exhaust would, which seems very small.

The difference between the generic and namebrand is that the generic ones blow-out, get loud as **** and possibly fall apart in a pretty short time-period.