Did you remove the fuel line that goes from the firewall to the fuel rail when installing the header? I would check to see if that is leaking. Definitely check for fuel leaks, it could cause a fire.
FR '11 FF Mod pick
FR '12 Carlisle Nifty Fifty Award/Best in Boost/Best 08-11/Finest 5 Pick
FR '13 Carlisle 1st Place Award 08-11 Focus/1st place 08-11 Focus (FR13 award)/FSWerks pick/Ford Racing pick/Finest 5 pick/Top pick in the finest 5