Mattax said

Have you had a chance to check it driving at 30 to 40 mph and at 60 to 70 mph? Doing so will help identify which circuit to focus on.


Very interesting. esp. if this is true at 65 mph

Engine dyno or chassis dyno? Do you have a file or printout of the pulls?

Yea. maybe. Always possible, and hard to predict absolutely. Dyno pulls were almost certainly done at wide open throttle.


* Leave the secondaries alone. They are completely irrelevant until the the throttle is much further open and rpms are up.
* Was the primary jetted 68 - > then tried 74s, seemed worse --> tried 72s?

A dyno pull with the AFR graphed will reveal whether the main airbleeds and e-holes are about right.
A wideband for what you are trying to figure out is hardly necessary. You know you're at the limit and they only way to figure out which circuit(s) to focus on is methodically change one thing and observe the effect. A logger with AFR, RPM, MAP and/or TPS is handy to track and see the relationships and how they change. So don't take it that I don't beleive they are handy tools, they can be.

I'm going to suggest two possibilities.
1. The main air bleeds and primary jet combo is such that the main circuit doesn't start early enough. A WOT pull in 3rd or 4th will often show that.
2. The idle circuit tapers off just a little too early.

If its really close, then slightly raising the primary fuel level may help. Just a 1/6 or 1/3 of a turn will make all low throttle slightly richer. My guess is that is too subtle of a change for the condition you are describing.

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