Uel header vs El header
 

Was doing some research, and somebody said on another forum that a uel header was causing his ecu to malfunction because of different pressure from the pistons. I don't know much about cars, but more than willing to learn. Anybody know if this will be a problem if I purchase a uel header? Or what's better to run, El header or uel header?

Dependent on the header design you will more than likely throw a CEL code which is why most companies recommend you tune your car after install. EL usually provides more power than a UEL but you lose the boxer rumble. I ran my Nameless EL headers vs a friend with Borla UEL headers. I pulled him in 2nd and 3rd, he pulled me in 4th. The gains wont be too significantly apart from each other so its basically going to come down to preference. Hope that helps.

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If they are both well designed headers their will be little difference in performance.
EL generally produce slightly more top end power
UEL generally produce slightly better midrange
only a few hp in it

Just pick the sound you like UEL for clasic subbie rumble .

Stock header has catylitic converter, if you put on catless headers either uel or el it will likey throw a cel code due missing cat. Catted headers either type should not throw cel code . You can get a O2 sensor spacer to hopefully stop the cel code.

To get max benifit from either type of header you need a tune, you might only get 5 hp gain without a tune but 15 hp with tune and better midrange and no cel code as tune will disable the cat efficiency cel code