Recently replaced plugs and coils to fix a high rpm misfire/sputter... which fixed that problem immediately and car has been solid ever since... until today...

Drove all day with no issue, then I just got home to park and idle is doing something weird. The rpms arent dipping or surging but I'm hearing a very slight stumble sound accompanied by a shutter through the car I can feel. It's so small you wouldn't normally be able to tell.

So plugs and coils are good, HPFP replaced less than 10k miles ago... and n18's really aren't subject to carbon buildup early on (I'm just under 50k)

The only thing that comes to mind is a possible vacuum leak maybe? But then again why would that trigger this tiny little stumble blippy shutter thing?

I also thought maybe I'm using too high of an octane? I use 93 and wonder if maybe since it only requires 89 it's more than it needs?

Please response with any thoughts thank you!!

 

i would guess vacuum leak. easy enough to check and rule that out as the cause.

 

But what is it about a vacuum leak that would cause this? And what's sucking air besides the intake/manifold?