You're not seeing anything extreme for a stock setup, and just keeping things fresh/clean as-is would be fine (MAF, plugs, etc.). The factory settings cause enough fluctuations and adjustments during boost that eliminating all KR is a chore.
Downpipe with a hi-flow cat would be a good addition for about $200, which may require adding an extension to move the rear O2 out of the direct stream and avoid a code (or O2 emulator, if you find one used). The u-bend and an older cat are going to be one of the best things to get out of your way. Aside from that, you're doing fine for a clean near-stock setup.
