Anyone with standalone ever get misfires under vacuum? Lately, my car has been starting to run rough, misfire and backfiring a lot when operating in vacuum. When I get into boost, it straightens right up and pulls strong / smooth, and wideband reads perfectly rich. When it misfires under vacuum, I'm seeing between 13.9 and 14.8 AFRs.

I don't understand what would cause a misfire in a situation where the mixture should be EASY to ignite, in comparison to being in boost, where it should be much more difficult to ignite. It almost feels like there's an injector that won't open quickly enough and is "skipping" pulses, but, I doubt it, 'cause it's backfiring like mad so there is unburned fuel. It really seems spark related.

Can a bad set of plugs 'cause this? I flooded the CRAP out of my car a few days in a row trying to tune the cold start maps once again. The car seems to run better in vacuum after boosting the crap out of it.

Could my plugs be too cold for my setup and not getting hot enough to clean off deposits or something?

I'd appreciate any advice.

Thanks!