P0153 CHRYSLER -changed sensor and code comes back?

Question

there is no noticeable exhaust or intake leaks. this is a 2008 sebring 2.7. overhaul great mechanical condition. there is not an engine miss, nor is there excessive usage of fuel, though when scanning you can see that the bank 2 sensor 1 is staying on the rich side too long. when you graph the two upstream sensors you can see the difference in there performance drastically. Its not that it doesnt go lean it just stays rich for about 2-3 seconds before going lean. which i know it should be switching from rich to lean roughly 16 times in a 20 second period. Long term adap on bank 1 is 2.9. on bank 2 it is 2.3. Anybody have any ideas. I am going to check injectors to see if one is noticeably different on pressure drop.