Under acceleration sometimes my car does a "sputter" almost like a loss of power of a second then continues. I changed my plugs recently and got s new air filter hoping it would eliminate it. Any advice?

 

And my boost gauge is telling me I'm only boosting around 12-13lbs when it was more like 15-16 before

 

Wonder if maybe you have some carbon buildup on the intake valves ? Any start up issues at all ?

Dealers are performing the walnut clean/polishing proceedures. There are tons of threads on this topic here. Do a search in Stock Problems and Issues section for 2nd Gen.

 

Sounds like it could be the issue with the high pressure fuel pump. It's a known issue by Mini so you might want to have them take a look.
Probably have to do the same myself since I'm seeing the problem too.