[Tony Curcio]

I used 4 of 11 pulls on this issue. The result was the opposite of what I expected.

The AFR for straight collectors was 12.47 and 12.48
The AFR for merge collectors was 12.20 and 12.18

So the mixture was richer as a result of installing the merge collector, the equivalent of .002 or .003 change to secondary metering rods.

There was a horsepower gain, about 4.5 average, with no other changes. It responded to being richened even further, so it isn't clear if the gain had more to do with needing to be richer in the first place, or the merge collector. We'll work on this some more at the track in the spring.