So I have an Evo 8 and it's tuned on speed density and drive great when not in vacuum, but when I am on the highway at around 4K normal driving or while I'm driving at any constant speed from 2k-2400 or 4K-^ I get really bad hiccups and the afrs jump does anyone know what the issue can be.

Mods are
port and polished head
tomei 280 pro cams
new oem valve seals
gsc 5041 spring and retainer kit
stm egr block off plate
arp l19 head studs
4" ets intercooler
ets licp
injen uicp
3.5" custom exhaust with vibrant muffler and resonator
hood dump
fp jb black ss housing
fp manifold
tial 38mm
k20 cop kit
omni 4 bar
3.5" intake with aem filter
walbro 450 pump
fic1100 high z injectors
aluminium radiator
comp stage 4 clutch kit with act streetlite flywheel
3 port grimspeed
act monoloc
mini battery kit with pc680 battery
innovate timer and wideband combo
Aem Wideband, Afr, and Oil Pressure gauges.




Spark plugs BPR8EIX



And plugs are gapped right

 

I am thinking it's my coils, but I have no clue.

 

I would check for boost leaks!

 

No boost leak holding boost. This only occurs when in vacuum.

 

Could it be because my bov is open while driving? Maybe I need a stiffer spring because I am only seeing this at like -10 psi or more.

 

My sti bov you to open while cruising and caused this exact same issue I would start there it was hard to diagnose because once I came to a stop or the rpm's dropped it would close off

 

bov

 

Maybe be a speed density glitch. Isnt there a jitter fix patch in tephra?