Strange stuff found in my fuel tank
 

So this weekend I changed the fuel pump on my '02 Yukon XL 2500 (180,xxx miles). The pump I replaced (GM Part) I had installed at the local Chevy dealer last March when the pump before that failed (non-GM part) and left me on the side of the road. This pump worked fine other than it was starting to get louder and louder and louder. The new pump (GM Part) is of course silent and is working perfect once again.
The strange part was when the old pump was taken out we found what appears to be chunks of molded silicone rubber in the bottom of the tank.
https://sphotos-b.xx.fbcdn.net/hphot...57501701_n.jpg

Could this be from the old fuel pump, insulation or padding from around the pump that caused it to become louder? The pump itself seemed to be loose in the plastic housing leading me to think it was vibrating. I've never seen anything like this before in a fuel tank. I've never run any additives in my fuel, other than Heet a couple times, and typically run 89 octane w/ 10% ethanol (cheaper than 87 octane here). Any thoughts?