OK I've been having an occasional P0170/P0173 (Merc 2017/2086) " (at idle speed). Enrichment over permissible limit" both banks.

Today for the first time I observed it: fully warmed up at a stop light the instant fuel trim on both banks went into 20's (usually around 3) bank 1 first followed by bank 2. As soon as left light it came right back down. Fuel pressure is 58, replaced MAF, replaced O2 sensors, checked for hose issues (but a vaccuum leak would make it go lean, not rich). About the only thing I can think of at this point is a leaky injector but not sure how a bank 1 injector would affect bank 2. Anyone have a different idea ? I do not have enough hair as it is.