Replaced Head Gasket Now Lopes At Idle

[89llx]

it does not stall, and runs good but this is a bone stock mustang and it lopes like it has an f cam in it


what can it be


looked for vaccum leak

 

[Dan_Soprano]

The firing order correct and all the plug wires seated properly?

 

[General karthief]

Is it surging, like rpms rising then dropping, not a steady idle?
Or does it have a steady idle and sounds like a race car?

 

[89llx]

found it i made a blocker plate for the EGR valve and fixed it