It could be a couple things and there are a couple of ways to fix it.
- If you stomp it and it goes lean, its generally accel pump.
-- Make sure its adjusted properly
-- You could go larger squirter to come on quicker but have the same amount of fuel
-- You could go with a blue cam to add fuel and come on quicker (there are others, but the blue usually works pretty well)
- If its a lean spike during a more gentle acceleration it could be PV or transition circuit
-- Make sure you don't have too tight of a PV, a vac gauge will help. If it opens at 6.5 and its stumbling as it passes 7.5, its too tight go up
-- Make sure your float level is high enough. Its not a fixed setting, raising it starts all circuits more quickly, so raising a little can get main jet fuel moving a little quicker, as well as all the other circuits
-- Low speed air bleeds can be made a little smaller, this will get transition fuel moving a little quicker, make very slight changes. .001 makes a difference in % of area
-- Primary throttle blade adjustment can be wrong too, if you are too deep in transition when you hit it, it wont enrich until the mains come in, also leaning things out.
-- You can even mask those issues with a good? pump choice, but that is sort of fixing a watch with a hatchet. Accel pump fuel is very coarsely metered and if its a PV or transition circuit problem, bathing it in accel pump fuel isn't a great fix, even if it works sometimes
- As far as fuel consumption, I would look at a few things
-- Make sure you have some timing at cruise RPM. Should be quite a bit, maybe up to 50, but low load, and lean, like at cruise, you need a lot for a good burn
-- If you reduce main jet size, realize that WOT may, not will, need more PVCR fuel, so if you jet down and your bog gets worse, odds are your PV is late or the PVCRs are already too small
-- Its perfectly fine to lower main jet if you offset with PVCR fuel, and often can help mileage quite a bit
Remember, WOT under power is easy, some combination of main jet and PVCR pretty much does what you need. Its the part throttle tuning that changes the rest of the curve and ends up where you need it at WOT that takes all the finesse.
Do a change at a time, take notes, and you'll get it to do whatever you want it to do