I bought a new 870 "tactical" a few years ago. I read on the AI&P Tactical site that its a good idea to change the extractor to non-MIM and Carrier Latch Spring. I also removed the Remington +2 extension and replaced it with a Wilson +2. The extractor took a little bit of fitting but other than that it was easy to replace the parts and it runs like a dream.
Although, this would be hard to pass up.