Originally Posted by malc
The pic is way too small to see any groove.
It's between the rear bolt hole and the front bolt hole on the passenger side. You can see the radius
where the straight groove starts just after the rear bolt hole if you are eye-ing from there towards the front bolt hole.
Here is the start of the radius circled in red: http://www.putfile.com/pic/7936403
In other words the wall thickness of the passenger side is thinner than it should be compared to the thickness of the wall of the driver side.
Only other thing I can figure out is maybe the base is warping once it gets hot but I didn't see any leakage of fuel anywhere?!?!