So my check engine light came on and I got back code P0411. I've got a 1996 f150 xlt 4.9 300. Any help would be greatly appreciated.

 

P0411 Secondary Air Injection Incorrect Upstream Flow Detected

Ford 1996 emissions manual, the computer throws P0411, after testing the AIR system. The system is tested by:
1. Causing a Rich condition at idle.
2. Commanding the AIR system to dump air into the heads.
3. If O2 sensors read lean, the test is passed. If no change in the O2 is detected, P0411 is thrown.

This thread may help you:
https://www.f150forum.com/f10/p0411-help-98481/