Intake Popping? WTH?

Just today during a cold start my intake started making like a weird muffled popping noise. It only does this until the engine has warmed up to normal operating temp. I’ve done a few things in the past couple of days that might have something to do with this:
-fixed my crappy idle by cleaning out EACV adjusting FIV, and replacing thermostat.
I ran it around for 2 days without hearing this noise, and now all of a sudden it starts. What the hell is it?
Its the intake on a b16 ls/vtec btw (just so i don’t get a wrong forum message).