reduced performance in version 2

Hello, I noticed a significant performance decrease with version 2.0.1 (boto3 1.3.1) relative to version
1.5.20 (boto 2.40.0). With version 1.5, a list operation of a bucket takes 3 seconds on average, while
with version 2 it takes 5 seconds on average. Previous version was downloading ~70GB in 15 minutes,
current version downloads ~40GB. An automated task that executes periodically a set of different
operations across multiple buckets and regions, took 5 to 6 times longer. Let me know if I could assist
somehow. Thank you.

Start by reproducing the reported bucket list and download operations with boto3 1.3.1 and boto 2.40.0 across the affected buckets and regions. Compare timings for the list operation and the automated multi-operation task; done means identifying a reproducible regression and documenting or testing the affected path.

Written by the indexing model from the issue text.