So I have a1996 f150 supercab with the 5.8L. I was wondering if I put headers on. Can I just leave the egr system there and not going to the header so I don't get a CEL?

 

Its not advisable to run without the EGR. You can get pinging (detonation) plus its a headache to try and diagnose anything further due to the fact Speed Density (SD) is so picky when it comes to removing any components other then the smog system. If you go to a decent exhaust shop they can weld in a Bung below the header so you can attach it there. Flex copper pipe works I haven't had any issues with the EGR system sense the headers.

There are several threads with a lot more information through out the forum try looking through a few and you will get a better idea as to what systems you can modify and what to avoid like the plague.

 

No you can't just let it hang because it will allow air into the intake where there should only be exhaust gas, and because the DPFE system on your '96 actually measures gas flow through the EGR tube you will get codes and a check engine light. Adding a fitting to the front header tube for the EGR isn't that difficult and the female end of another tube works well as the fitting, this is something you can grab at a junkyard.