Is it fluttering just on lift from part throttle? If so, it's fairly normal and harmless with the low pressure at part throttle. Probably more due to your metal intake than the BOV anyway. That BOV should be adjustable though (doesn't require new springs) by turning the top. Tighter = more preloaded on the spring which means later venting at higher pressure and a faster close. You want it about as tight as it will go without fluttering on WOT shifts (when it actually matters).
And Hpfp + rem + accessport +racepipe (90% of gains from downpipe, <5% of install difficulty) has my vote.
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