2004 M6 V6 hesitation

[bbmazda]

Help with troubleshooting - M6 sportwagon w/85,000 miles. Hesitation and sputter under slight load and more pronounced on shift from 4th to 5th. P0171 and P0174 codes. Replaced plugs, PCV Valve and hose and cleaned the MAF. the intake manifold and EGR tube had a lot of oil residue. The CEL has been off since, but the hesitation is same or worse. My next step is to check the EGR function and clean the injectors. Any other suggestion? How can I check the EGR?