So i have mods in sig. I do not have my header on yet and i am going to get tuned for meth and i just got the wideband in so he said he can use that to tune my a/f. Now will it make a diff in the tune after i put my header on since i will not recieve my header until after the tune?

 

Exhaust mods, from what I have been told, do not really effect the tune. Only the intake/engine components do.

IIRC

 

When I added the exhaust and extruded manifold it had an effect, leaned it out a bit, no codes were thrown or anything like that. Only had it that way for a week before I retuned it.