I have attached the catted UEL plot bellow. But before you jump to conclusions based on numbers...
The car already had a perrin 3" exhaust, nameless catted FP/OP combo, and a drop in filter. This car
was an automatic. This dyno reads extremely low (something like 20-25% lower than a dynojet). Auto's run 120-130WHP on this, manuals are 130-140WHP.
The baseline was his exhaust, FP/OP, and drop in filter after dyno tuning, the header was installed the next day and re-tuned using similar techniques. The baseline peak was 132WHP. This was consistent through multiple pulls. The final numbers ranged from 147-150WHP so I plotted one of the more "average" results rather than the highest. (It was pretty warm out, even though this dyno does great at compensation when you break into 110F weather the car likes to start to give you hell).
If you notice the power gains were at nearly every RPM... so yes there was a torque dip but there were gains in the torque dip. But from what I have seen the UEL headers from multiple companies are giving nearly no gains at about 5kRPM where as this one is giving a stead 2-5WTQ through that entire region.
I forgot what the peak WTQ was on the tuned baseline but it was a WTQ gain of ~10-11%. The WHP gain was 16WHP netting ~
12% WHP gain. This is actually quite decent... This car was starting to get closer to a lot of the tuned manual cars peak gains, and as you can see the tq was barely falling at 7,500RPM. Overall this header is actually quite decent. Even if you look at just the WHP gains considering this is an automatic and you compare it to higher reading dynos this is still a very decent gain.
