Funky AFR hump, any help

[valley318]

Hey guys,

new to the forum... Dyno'd my car the other day and there is a strange hump at 4K it goes lean and comes back to normal after about 500 - 700 RPM's... It is completely stock... I have check everything and so has my local mechanic and can't find ANY leaks...

Is this typical of the engine? its consistent and EXACTLY the same EVERY time.

any help would be appreciated.

[tjts1]

There are some vacuum hose connections hiding underneath the intake manifold that are impossible to spot without taking the whole thing apart. See the link in my signature.
good luck
PS: What numbers did it pull on the dyno?