P0172 and P0175 fuel trim readings

What is your question?

basically, I have the two codes above and started to test to see when it would act up. it starts off at no fuel trimming won't start unless you rev it to 1500 rpm. it doesn't increase during the rev but after it returns to idle it drops to -28.1 on both bank 1 and 2. after idling for about a minute and a half it returns to 0 fuel trim and won't act up unless revved again to above 1500 rpm. what seems to be the culprit for this?

What makes this problem better or worse?

worse when revved

How long has your 2001 BMW 330Ci had this problem?

half a year