Different Indian consulates in USA use different application forms for applying for PIO card:

Indian Embassy, Washington DC
Indian Consulate, New York
Indian Consulate, Chicago
Indian Consulate, Houston
Indian Consulate, San Francisco

PIO Application Form

PIO Application Checklist
PIO Application/Renewal form (Form O)
Form to be completed along with application for PIO card (Form U)
Affidavit for child below age 18 (Form P)
For Foreign national applying for PIO card as spouse of Indian national/PIO/OCI (Form S)
  Also See Renunciation Form

PIO Application Form

PIO Application Form
PIO Application for Miscellaneous Services

For residents of India, to be filed at FRRO Office

Note: Complete information about PIO card