Did you ever solve this? Having a similar issue on my FBM kit

No, I never had time to look into it further due to another project car.

I have custom tune, so was going to try a base FBM tune to see if it does the sane thing. Also, was thinking if could something with MAF settings.

What’s your specs and are you using a FBM base tune or custom?

I've been through two custom tunes, but haven't been able to resolve this issue. Have been told by my tuner it's due to instability in the maf sensor which is pretty common with the fbm kits. My issue goes away when I'm on ethanol though so it seems to be just a problem with pump gas.

I'm running their premium kit with a gtx3076r, fx400 clutch, fbm walbro 485lph pump, id1000 injectors, motoeast flex fuel kit, etc...

Mine does it on ethanol as well, btw have you tried a base FMB tune? Basically FBM base gas tune taking into account the bigger injectors and map sensor?

I have not tried their basemap. I couldn't get my car to start on the basemap so I had it towed to their shop, found out my map sensor was faulty but just went straight to the Dyno from there.

I would not recommend running a basemap for any longer than necessary. They're really only designed to get your car to the shop for a custom tune

fellas its your base idle in gear timing, set too high. return to stock timing for these tables to resolve

Had the exact same issue. The car was running fine and one day it just stalled on the freeway and wouldn't start. Car would only started with little gas and I had to keep revving the engine. But then I notice when stop and left in gear the engine rev up to 3000rpm by itself, and went back to normal idle when in neutral. The problem went away after a day or two, still kind of worry about it tho.

Mod: Edlebrock supercharger with dbox( maf sensor), straight e85,

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That does not explain why it happens out of the blue to people on a tune they've been running without issues.

Not sure thats my issue as it only happens while im moving. If I am stopped, in gear, my idle is normal.

Thanks, I will look into it in a few months when I get warmer weather over.

I also have a base FBM tune which I will test just low speed to see if it’s a tuning issue or something else