I did have a slight issue with the dust cover for my low beams. The stock dust covers *almost* fit, but if I secured them they would push on the bulb, and it would force the reflector out of the adjuster. It was easy to fix though, just needed popped back in.
As a result, I purchased some 85mm universal aftermarket dust covers. They give plenty of room, but didn't fit very well. I had to use a little electrical tape to make sure it was on there right. They also give more room for the wires I guess, so they haven't melted off yet, as far as I can tell, anyway.
Ok cool... I was wondering if aftermarket dust covers would be in order, but I did something else... I have a supply of fabric tape from a company called Nitto Denko. It is like electrical tape, but fabric like, and it is supposed to be heat resistant. So I pulled the lamps and wrapped 2" of wire with the tape and put it all back together.
Last night was my first ride in the dark and let me say, these things are great. Signs are much brighter and pop more, I can see deer standing off to the highway and have more reaction time, and overall, the road is well lit. This should be on the top of everyone's mod list. No flashes from other drivers either.
Went out a little bit ago and checked the wiring... all is good. So the only advice I would give on buying LED bulbs for 2006-13 and 14-16 Impala limiteds, with stock headlamp assemblies, would be to find a bulb where the power wire comes out at the bottom of the bulb, 90° to the heatsink, and not directly at the back, right in the middle of the heat sink. If you can't avoid that, then be prepared to wrap the wire in heat resistant material to protect it from the heatsink.
These superbrightleds bulbs do a good job otherwise. I may indulge in high beams down the road, but I never really used them that much to begin with, so it would be mostly for aesthetics.